I dont' know how to use KMZ loader.
However, if check the Layers button on Google Earth you'll see a My Maps option. You need to sign up for a My Maps account. After that any .kmz files you store on that site will be available for your use in Google Earth on the iPad.
I can't tell you more than that, since I've never had a reason to get the account and try it.
Good luck.
One other thought. The KMZ Loader probably syncs with My Maps on Google; so if you've already created one be sure to use it instead of making a new one.