Here's what I currently have. I have tried it with just the CEON stuff I have tried adding a / in front of the index as described on the installation check page also.

Code:
###############################################################################
# Add custom headers and options
###############################################################################
# Notes:
#
# Examples: Adding IE compatibility / edge flags, language and encoding flags,
# php or suphp directives, configure other Apache modules such as page_speed,
# and enable or disable Apache httpd options.
#
# Do NOT configure anything directly relating to physical or virtual resources
# in this section. These should be addressed later on in this file.
###############################################################################
#Options -Indexes

###############################################################################
# Enable mod_rewrite processing using the rules in this .htaccess file
###############################################################################
# Notes:
#
# <IfModule> should be avoided at all costs. If mod_rewrite is not available
# it is almost always better to return HTTP 500 status. This way we see there
# is an issue as soon as the .htaccess file is uploaded.
#
# For mod_rewrite to work, the Apache server option to allow symbolic links to
# be followed must be enabled. Most providers supporting mod_rewrite will
# already have it enabled for you, but if your rewrite rules are not working
# you can un-comment the first directive below to manually enable the option.
#
# Don't forget, mod_rewrite directives are processed in order until a matching
# RewriteRule with the [L] flag is encountered. So the more specific a rule is
# the closer it should appear to the top of this file.
###############################################################################
#Options +FollowSymLinks
RewriteEngine on

###############################################################################
# Tell mod_rewrite where this file is relative to the server document_root
###############################################################################
# Notes:
#
# This directive should only be enabled if this .htaccess file is not placed
# in the document_root (usually public_html, www, or web) of the (sub)domain.
#
# An easy way to determine the location relative to the server document_root is
# to look at the URL used to access a file in this folder. For example if you
# access a "page" in the same folder as this file by typing in the URL
# "www.mydomain.com/myfolder/index.html" then "myfolder" will be the location
# of this file relative to the server document_root.
#
# Another quick and easy way to determine the correct setting for this is to
# look at the defined value for DIR_WS_CATALOG and DIR_WS_HTTPS_CATALOG in
# Zen Cart's configure.php files. All three values should match.
#
# Don't forget the leading and trailing /. This directive requires both!
###############################################################################
#RewriteBase /shop/


###############################################################################
# Redirect if request was for index.php (no query)
###############################################################################
# Notes:
#
# This is only required if the site generates references to index.php with no
# parameters. This rule will force a 301 redirect to the site root when a
# request is made for "/index.php" with no query terms (?key=value).
###############################################################################
#RewriteCond %{QUERY_STRING} ^$
#RewriteRule ^index\.php$ / [R=301,L]


###############################################################################
# Add any custom 301 redirects
###############################################################################
# Notes:
#
# In general these should be few and far between. If you use a RewriteRule
# be sure to add the L flag to let Apache mod_rewrite know to stop processing
# and skip any RewriteRules defined later in the .htaccess file.
###############################################################################


###############################################################################
# Redirect if request was for index.php (with or without query)
###############################################################################
# Notes:
#
# This is a performance optimization. If the request is for index.php simply
# pass the request on and do not process any other mod_rewrite directives in
# this file.
#
# Basically this avoids the overhead of checking if index.php is a real file
# or directory (used in subsequent mod_rewrite rules) before sending the
# request to index.php.
###############################################################################
RewriteRule ^index\.php$ - [L]

<IfModule mod_deflate.c>
  # Compress HTML, CSS, JavaScript, Text, XML and fonts
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
  AddOutputFilterByType DEFLATE application/x-font
  AddOutputFilterByType DEFLATE application/x-font-opentype
  AddOutputFilterByType DEFLATE application/x-font-otf
  AddOutputFilterByType DEFLATE application/x-font-truetype
  AddOutputFilterByType DEFLATE application/x-font-ttf
  AddOutputFilterByType DEFLATE application/x-javascript
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE font/opentype
  AddOutputFilterByType DEFLATE font/otf
  AddOutputFilterByType DEFLATE font/ttf
  AddOutputFilterByType DEFLATE image/svg+xml
  AddOutputFilterByType DEFLATE image/x-icon
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/javascript
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/xml

  # Remove browser bugs (only needed for really old browsers)
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4\.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
  Header append Vary User-Agent
</IfModule>

<ifModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file .(html?|txt|css|js|php|pl)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</ifModule>

<ifModule mod_headers.c>
    Header set Connection keep-alive
</ifModule>


# ######################################################################
# # MEDIA TYPES AND CHARACTER ENCODINGS                                #
# ######################################################################

# ----------------------------------------------------------------------
# | Media types                                                        |
# ----------------------------------------------------------------------

# Serve resources with the proper media types (f.k.a. MIME types).
#
# https://www.iana.org/assignments/media-types/media-types.xhtml
# https://httpd.apache.org/docs/current/mod/mod_mime.html#addtype




# ----------------------------------------------------------------------
# | Reducing MIME type security risks                                  |
# ----------------------------------------------------------------------

# Prevent some browsers from MIME-sniffing the response.
#
# This reduces exposure to drive-by download attacks and cross-origin
# data leaks, and should be left uncommented, especially if the server
# is serving user-uploaded content or content that could potentially be
# treated as executable by the browser.
#
# http://www.slideshare.net/hasegawayosuke/owasp-hasegawa
# http://blogs.msdn.com/b/ie/archive/2008/07/02/ie8-security-part-v-comprehensive-protection.aspx
# https://msdn.microsoft.com/en-us/library/ie/gg622941.aspx
# https://mimesniff.spec.whatwg.org/

<IfModule mod_headers.c>
    Header set X-Content-Type-Options "nosniff"
</IfModule>

# ----------------------------------------------------------------------
# | ETags                                                              |
# ----------------------------------------------------------------------

# Remove `ETags` as resources are sent with far-future expires headers.
#
# https://developer.yahoo.com/performance/rules.html#etags
# https://tools.ietf.org/html/rfc7232#section-2.3

# `FileETag None` doesn't work in all cases.
<IfModule mod_headers.c>
    Header unset ETag
</IfModule>

FileETag None

# ----------------------------------------------------------------------
# | Expires headers                                                    |
# ----------------------------------------------------------------------

# Serve resources with far-future expires headers.
#
# (!) If you don't control versioning with filename-based
# cache busting, you should consider lowering the cache times
# to something like one week.
#
# https://httpd.apache.org/docs/current/mod/mod_expires.html

<IfModule mod_expires.c>

    ExpiresActive on
    ExpiresDefault                                      "access plus 1 month"

  # CSS
    ExpiresByType text/css                              "access plus 1 hour"

  # Data interchange
    ExpiresByType application/atom+xml                  "access plus 1 hour"
    ExpiresByType application/rdf+xml                   "access plus 1 hour"
    ExpiresByType application/rss+xml                   "access plus 1 hour"

    ExpiresByType application/json                      "access plus 0 seconds"
    ExpiresByType application/ld+json                   "access plus 0 seconds"
    ExpiresByType application/schema+json               "access plus 0 seconds"
    ExpiresByType application/vnd.geo+json              "access plus 0 seconds"
    ExpiresByType application/xml                       "access plus 0 seconds"
    ExpiresByType text/xml                              "access plus 0 seconds"

  # Favicon (cannot be renamed!) and cursor images
    ExpiresByType image/vnd.microsoft.icon              "access plus 1 year"
    ExpiresByType image/x-icon                          "access plus 1 year"

  # HTML
    ExpiresByType text/html                             "access plus 0 seconds"

  # JavaScript
    ExpiresByType application/javascript                "access plus 1 hour"
    ExpiresByType application/x-javascript              "access plus 1 hour"
    ExpiresByType text/javascript                       "access plus 1 hour"

  # Manifest files
    ExpiresByType application/manifest+json             "access plus 1 year"

    ExpiresByType application/x-web-app-manifest+json   "access plus 0 seconds"
    ExpiresByType text/cache-manifest                   "access plus 0 seconds"

  # Media files
    ExpiresByType audio/ogg                             "access plus 1 month"
    ExpiresByType image/bmp                             "access plus 1 month"
    ExpiresByType image/gif                             "access plus 1 month"
    ExpiresByType image/jpeg                            "access plus 1 month"
    ExpiresByType image/png                             "access plus 1 month"
    ExpiresByType image/svg+xml                         "access plus 1 month"
    ExpiresByType image/webp                            "access plus 1 month"
    ExpiresByType video/mp4                             "access plus 1 month"
    ExpiresByType video/ogg                             "access plus 1 month"
    ExpiresByType video/webm                            "access plus 1 month"

  # Web fonts
    # Embedded OpenType (EOT)
    ExpiresByType application/vnd.ms-fontobject         "access plus 1 month"
    ExpiresByType font/eot                              "access plus 1 month"

    # OpenType
    ExpiresByType font/opentype                         "access plus 1 month"

    # TrueType
    ExpiresByType application/x-font-ttf                "access plus 1 month"

    # Web Open Font Format (WOFF) 1.0
    ExpiresByType application/font-woff                 "access plus 1 month"
    ExpiresByType application/x-font-woff               "access plus 1 month"
    ExpiresByType font/woff                             "access plus 1 month"

    # Web Open Font Format (WOFF) 2.0
    ExpiresByType application/font-woff2                "access plus 1 month"

  # Other
    ExpiresByType text/x-cross-domain-policy            "access plus 1 week"

</IfModule>

## BEGIN CEON URI MAPPING REWRITE RULE

RewriteEngine On

# Don't rewrite any URIs ending with a file extension (ending with .[xxxxx])
RewriteCond %{REQUEST_URI} !\.[a-z]{2,5}$ [NC]
# Don't rewrite any URIs for some, popular specific file format extensions,
#   which are not covered by main file extension condition above
RewriteCond %{REQUEST_URI} !\.(mp3|mp4|h264|woff2)$ [NC]
# Don't rewrite admin directory
RewriteCond %{REQUEST_URI} !^/backend [NC]
# Don't rewrite editors directory
RewriteCond %{REQUEST_URI} !^/editors/ [NC]
# Don't rewrite .htpasswds directory
RewriteCond %{REQUEST_URI} !^/\.htpasswds/ [NC]
# Don't rewrite .well-known directory
RewriteCond %{REQUEST_URI} !^/\.well\-known/ [NC]
# Don't rewrite bmz_cache directory
RewriteCond %{REQUEST_URI} !^/bmz_cache/ [NC]
# Don't rewrite min directory
RewriteCond %{REQUEST_URI} !^/min/ [NC]
# Don't rewrite pzen_includes directory
RewriteCond %{REQUEST_URI} !^/pzen_includes/ [NC]
# Don't rewrite logs directory
RewriteCond %{REQUEST_URI} !^/logs/ [NC]
# Don't rewrite zc_plugins directory
RewriteCond %{REQUEST_URI} !^/zc_plugins/ [NC]
# Handle all other URIs using Zen Cart (its index.php)
RewriteRule .* index.php [QSA,L]

## END CEON URI MAPPING REWRITE RULE