I highly disagree with that extension.
You could just scan vor zip files and catch the file list and look for a special index file.
This would not force us to rename zip files.
(Do we really need another zip file-format - besides .jar and maybe several others?)
Can one of the site mods add .lext as an approved upload file extension?
You are already expieriencing the first problem with that choice.
Or even more easy: filename.lext.zip