I think we've already resolved this via email, yes? IIRC, your testers were only unzipping the main download file itself, and neglecting to unzip additional files nested inside?
To avoid that sort of problem with real buyers, we'd recommend not having any nested .zip-files-inside-.zip-files at all, especially considering that zipping a file that's already zipped doesn't make it any smaller. Instead, arrange all your files fully-unzipped into a clear set of subfolders inside a master folder, then just zip that whole master folder at once.
