The TouchPro is a resistive touch screen, and therefore cannot accept more than one touch screen input at a time.
The G1 (and the iPhone) is a capacitive touch screen which allows multiple touch inputs at the same time. This also allows for a brighter screen, but at the expensive of being able to use a regular stylus.
http://en.wikipedia.org/wiki/Touchscreen
The only part of the TP that can accept multiple touches would be the bottom area underneath the screen because those buttons at the bottom are in fact a capacitive touch entry area, Unfortunately, I don't see that area being very effective for multi touch zooming as we already have the touch sensitive zoom wheel which does the same thing.