Analogue zoom is no longer working when using TrackIR because the two key bindings that allow this to work have been removed from DayZ Alpha.
The two key bindings are:
Zoom In (Continuous)
Zoom Out (Continuous)
These key bindings are present in Arma3 and Arma 2 and I can confirm working (as did Natural Point who make TrackIR (web forum post here - http://forums.naturalpoint.com/viewtopic.php?f=4&t=12506&p=57534)