I’m learning about KML/KMZ files, where KMZ is basically a .zip file renamed as .kmz. The problem is that these .kmz files cannot be opened using the default Mac unzip utility. When you try to open the .zip file, it creates a new file called <originalfile>.zip.cpgz. Opening the .cpgz file yields a copy of the original zip.
The solution is to use Springy, a zip utility for Mac (free trial, ~$20 to buy). It handles the file perfectly:
Edit: Found an alternative approach here. Basically, rename the file .rar instead of .zip and the Unix unzip utility can handle it.
I’ve written a script to incorporate this; find it as a gist here.