Marble Blast STOP II Initial Release - Version 1.0

Well, you install the mod by launching an .exe executable (or just extracting the .zip file) in Windows, but in MacOS, you install either with an .app bundle or a .pkg package (they may come in a .zip file). Not sure with the MacOS one because I don't use Mac computers.

Additionally, the Mac version no longer runs on any of the modern Mac devices due to the lack of 32-bit support. And as Pasta said, the Windows version has an exe file which you use to run the game. Mac applications do not have these exe files, instead the game binaries are located in <root folder>/Contents/MacOS directory.