I'm not going to say what I feel like saying to that "Are you sure?" comment other than to say that I'm 100% positive. This isn't my first ride in this rodeo.

I just put my Daily Comic PA in the Install\Module directory and went the Module Definitions page and it's sitting there at the bottom of the screen waiting for me to check it and click on "Install Selected Modules". I also made a copy of the .zip and renamed it with the .resources extension and both show up. I could see where the DNN code has been written to automatically installs the .zip files when it's setting up the portal initially but once it's up and running it doesn't care what the extension is, it'll show up in the module list at the bottom of Modules Definitions. You can give it any extension you want and it'll show up there (I tried .rar and it showed up) but I doubt anything will install unless it's named .zip or .resources.