In some cases, the default Mac utility may fail when unzipping your restore. In this case you will want to use The Unarchiver:
1. Visit https://theunarchiver.com and click 'download'
2. Go to the downloads folder in Finder, and double click TheUnarchiver.dmg.
3. This will open the installation window. Drag The Unarchiver icon to the Applications folder icon.
4. Right click on the restore file, select 'open with' and choose 'The Unarchiver'. You can then create a new folder to place the restore in.