I wouldn't defrag the ppu, there's really no reason to.
As far as Zone Filling, I've only ever used it on my system drive. I suppose you could use it but it would really slow the defragmentation down, and is mainly for grouping your system files on the fastest part of the drive, followed by program files, followed by data you don't access much. I've got 20TB of media files in my array, so grouping would be pointless.