The 2007 CSC Rules have not been posted as far as I know. We only ran the FZ last year, or at least that was all the local tracks and shops were stocking.
The difference is in the shape of the tire. The MZ are square in appearance and the FZ are more rounded on top. The FZ was a better tire to tune with, and wore a lot better than the MZ.
The MZ looks like a rental kart tire, but with softer compound.
Hope this answers your question.