If you find, as I did, the Q+T+Reset function to be somewhat mysterious (I did... seemed to take forever so I gave up and NAND-restored) the same function seems to be available in the menu that pops up with OK+Reset, as "Update"
Purely speculation, but Q+T+Reset may only work for flashing a default sharp rom, and the "Update" may be selective about what is being updated (for instance, can be used for updating just a the kernel). If someone can correct me terrific, that's just been my observation.
If you're asking about your first flash, you probably haven't come across the diagnostic menu yet, which is VERY useful when doing all this scary flashing back and forth. For this, you use D+P+Reset, and will get a beep and a graphical menu. Scroll right with the D-pad until you are on page 4/4 (this confused me to no end the first time because it's also a four, like the "4. Update" on the OK-Reset menu, and in that case you scroll DOWN) and then there will be two options for NAND Backup, and NAND Restore. These are absolutely essential if you want the z to be anything but a toy while you are playing around with the different roms that almost_work. I screw around and break so much stuff that I back up to a cf at least every two days, and always right before any big "Project." I have always been able to restore to what I had before I started messing.
