Just because you have 7-zip does not mean you are using it. When you double-click on a zip file in Windows, you are using Windows File Explorer to look at its contents. Try right clicking on the file and opening it with 7-zip, instead. Unless you are still using a very old version (19.1 or older) you will see what is being discussed.
LOLWUT??????
First off, you have no idea what I did or didn't do. You can't speak for that. What I can tell you is I've never double clicked on the file. I use the dropdown submenus. Directly under 7-Zip. I do this because mainly I don't personally like using the Windows extractor.
I've inspected directly with the 7-Zip dropdown menu that opens the 7-Zip window. I've also extracted via the 7-Zip dropdown submenu. NOT the Windows one. The only thing you could be correct about is that I am using an older version of 7-Zip. Wow, and it has no problems! So the file isn't the problem.
In the newer version, the files aren't named with slashes. Instead, there's a dot. In any way that you view the file with Windows or an older version of 7-Zip, everything looks normal with its structure. When you're viewing in file explorer, everything should be as is. If the version you're using 7-Zip makes the file look funny, it's not the file. There's something wrong with the 7-Zip program you're using.
But again, as I've pointed out, the game is Windows only, even on Steam. There's no Linux compatibility, so I wouldn't even come close to thinking it has anything to do with any quirks of Linux.
But even if I went by what you think I was using, and extracting with the Windows extractor, it still had the normal result a with the older 7-Zip that I'm using. Therefore, the sum of these facts would tell me only the newer 7-Zip has issues with handling zips, but it's not the zip file itself. So, that's basically down to user error. Any problems you're having with this is either you're using a bad extraction program that can't handle compressed files, or you had a bad file to begin with that no zip extraction program can run with that file, which is highly not the case here.