Oh, I think you got me a bit wrong here. I don't have any problem with having to unzip the archive. It's that - inside the zip file there is an .app file - an os x executable that one should be able to run, just like an .exe file on Windows. But the system says that the .app file is corrupted (like one the screenshot I shared in my first post) and to actually run the game, you have to open the app package contents (which is not a standard thing to do) and find the game executable hidden in a not really obvious place.
But, dunno, it might just be a problem with my mac so feel free to ignore this if no-one else reports this.
All best!