Re: ZR TUNING HEAD PROBLEM
If you look at the back of the bridge, you'll see that the saddles are all at different heights. If you make the fine tuners 'neutral' by making them flat across the top, the middle strings get less adjustment upwards than they would otherwise. Coupled with string guage and intonation, which both affect the amount of pitch you can get out of the fine tuners, this might be your problem.
Regardless, I've got 2 guitars with ZRs, one a 7 string, and there is ample adjustment range on both provided the strings are put on properly and stretched.