If you're regularly having to disable the .htaccess security settings, then your problem would appear to be related to how your hosting company has configured their server.
Have you discussed this matter with your host?
Have you reviewed the server errorlogs to see what the server is rejecting?
Have you tried doing the same thing on a different server configured by a different hosting company who has a better handle on security configurations that doesn't prevent the operation of the security protections provided by the default Zen Cart files?




