To build Zoom for OS X, place CocoaGlk in here. You can obtain CocoaGlk via 
git as follows:

      git clone http://code.logicalshift.co.uk/zoom/cocoaglk.git CocoaGlk

You will also need to download suitable versions of git (the interpreter,
not the version control system) and glulxe. Place the source for these 
interpreters in the CocoaGlk/glulxe and CocoaGlk/git directories.