TrackIR zoom feature(?)

[sniperton]

Head-tracking changes the position and the direction of your view. It's equivalent to your hand holding a camera.
Zooming changes the field of view of your view, in much the same way as the zoom function of a camera does. It's equivalent to the adjustable lense of your camera.
The first simulates the movement of your eyes, the latter simulates the magnifying effect. They have nothing to do with each other.
Answer: no proper zooming is possible through head-tracking.