Mac files are usually unzipped by default. However, the file is showing as an application, and not as a .dmg disk image. For applications containing a lot of files, it is better to use a .dmg.
When attempting to launch the Mac application I receive the following error: "The application Base Dolphin Mac OS can't be opened". Sorry I can't be more specific than that. Such a shame, because I really wanted to give this game a try.
I really love the game because it's very addictive. This is my favourite game genre and it works very nicely on the mac. Keep up the great work. Well done.