Working on my local copy of ZC v1.50
Got this mod installed and ran the Ceon URI Mapping Installation Check, no errors found.Yippie, right?
Meh...not so much.
Re-mapped products don't show up, getting 404 error messages.

If using a .htaccess file

If placing the rule in a .htaccess file, the .htaccess file into which it should be placed is the site root's .htaccess file, which should be created if it doesn't exist:

G:/xampp/htdocs/.htaccess

Although the store is in a subdirectory, the .htaccess file into which the example rewrite rule should be placed is NOT a .htaccess file within the Zen Cart folder, the rewrite rule below is for the site root's .htaccess file - place it in the above file!
If using an Apache VirtualHost Directive

If the store runs on a server using Apache and it is possible to modify the VirtualHost Directive for the store, then the rule can be modified and entered into the VirtualHost Directive for the store.
Probably outside the scope of this thread......but how do I "create" a .htaccess file?