You don't care whether or not the hosting application program does zoning. You set up your presets in Pianoteq to play in the areas of the keyboard where you want. You are only using the host program to bring up a different instance of Pianoteq for each track you have set up.
Your light will turn on any minute now! (just kidding) Have fun!. You can listen to an example of this very technique in the Grotrian demo page: Fractals That demo piece includes 1) Grotrian, 2) Vibraphone, 3) the Acoustic bass preset in Logic 8 (a General MIDI sample), and 4) one of the normal Pianoteq presets that are voiced - Piano split bass. Fractals was recorded as a layer - not multi-tracked. This is the very thing you are trying to figure out how to do.
Hope this helps,