have you tried checking your PC's Sounds and Multimedia Properties (Control Panel)? Under the Audio tab, see if you can find your Z-tek (or Yamaha) under the Preferred device (MIDI Music Playback).
I got the DTX Mania a few months back. i tried installing it but it seems that its not working with my electronic drums, so i just removed it from my PC. medyo tamad ako that day.
then i saw this thread the other day, so i tried installing DTX mania again, connected my dtxpress to my PC via the yamaha usb to midi. set the yamaha usb-midi as my preferred device for MIDI music playback and now i can play the game with my electonic kit.
problema lang puro dream theater yung nakuha kong dtx files so medyo mahirap laruin.