I don't think you read the install instructions that come with zencart...

One of the fist things you must do when you have FTP'd all the files to the server, is configure the CHMOD permissions.

Here is the actual text of that instruction:

Set Permissions on folders
Now, change the permissions on the following directories to 777 (read/write/execute).

/catalog/cache
/catalog/images
/catalog/includes/languages/english/html_includes
/catalog/media
/catalog/pub
/catalog/admin/backups
/catalog/admin/images/graphs
The one you need to pay attention to in this instance is

/catalog/includes/languages/english/html_includes