Steam uses ZDP.exe as well to confirm the game exe zdp release date encryption, so far the trainer exe (First one.) has worked just fine with that. (There's also a disc based version using DR2Launcher.exe and SecuROM plus a modified exe as far as I know, xlive.dll from the crack can be used to remove life on any other copy if wanted but trainer seems to work fine with it enabled as well.)
Could differ in other regions I guess but it's no problems here.
1. Ultimate Trainer - Does NOT work for STEAM release of the game.
2. Ultimate Trainer (RETAIL+DIGITAL) - DOES work for STEAM release of the game.
If #2 - RETAIL+DIGITAL does NOT work for you then you (as already said by Caliber) likely have software or settings blocking it from working on your pc - i.e. antivirus (which is fixable), firewall (which is fixable) etc etc.