The ZOOM Track is Actually Part of the Screen sensor
 

I was touching the screen in the web browser and tried to zoom at the same time, and to my surprise the screen jumped as if i was touching in in two places. So i got out the stylus and tried to zoom and it did. i was still not able to touch the screen at the same time. One of the complaints with the pro and diamond was the buttons and d pad being capacitive...ish. HTC must have listened the complaints.

In more playing around i opened notepad and was able to draw with the zoom slider.