I've never used my Z-Zero Plate and I've read many posts on people having problems of one sort or another, so read on.
Using my experience from the CNC machinist trade here is my technique on the ShopBot:
I have a wireless Keyboard which allow me to bring it right next to the Spindle and the table top.
1. Using the Keyboard, move the spindle to a convenient place on the work.
2. Move down in Z until the bit is approximately .500 inch from the surface.
3. Place a .500 thick Brass or Alum block next to the bit.
4. Slowly increment the spindle up or down (in .001 or .002 increments) until the bit just touches the block, moving the block under and away from the bit until you feel a slight drag.
5. Using the VA command, tab down to the Z line and enter .500.
This process take only a few minutes and I never have to deal with the Z-Zero Plate, in fact, it is tucked away somewhere else out of sight and mind.
I use this same technique to set X and Y by entering in 1/2 the bit diameter, with the appropriate +/- sign, depending which side of the work you are on.
George Kelly