I GOT THE SOLUTION! Me too for about 2 years I've been trying again and again to sync my zune but was always freezing!!!
there are 2 things you can do to help sync without freezing, even if you have 4000 songs at once!
Plug the zune at the back of the computer and not the front: better power supply
Put an ice pack around the zune to cool it down (that really works!)