7z can open both zip as well as rar files. I dont think zip can open 7z files. It can open rar files though.
winrar can open all files as well, but you can not edit 7z archives with winrar.
We use 7z here for most of the archives here as it simple packs the files the most compressed compared to the others. What program you use to open them does not matter. As long is it actually can work with the files and you like the program it will do ;)
i made a 31st mod folder and inside that i made an addons folder. i put the .pbo files inside the 31st mod folder
The mod folder should be called exactly that name, not 31st, or whatever. But exactly the same.
Also remove the space after "=", it should look like this:
Open the editor and see if the 31th units/map/what not can be found in the editor. If so its working.