Adding the extension in es_systems.cfg is unlikely to make them work, just make them show up. As far as I know retroarch and most other emulators dont load .7z
You would be best to unzip (except mame of course)
If you want to edit the file, use PuTTY to SSH to the Pi.
RetroPie help guides --> https://goo.gl/Yfy8kj
Please read this before asking for help --> http://goo.gl/eLErnl