Hi guys I recently acquired the Rock Band Midi Adapter for the Xbox 360. They're available directly from Mad Catz and also Amazon.
I've tried it with the Zendrum LT and pretty much everything works. I still have not bought a foot pedal to act as a hi-hit pedal, I could use some suggestions on compatible pedals if any of you know.
Otherwise all the triggers work. I went to the Rock Band forums to look for a MIDI implementation and found this graphic that has a table of MIDI note values and CCs for configuring MIDI instruments for compatibility:http://img811.imageshack.us/img811/1010/rbmpmidinotemapping.jpg
A bunch of things I've learned so far...
It is important to always play in Pro Drums mode when using the Zendrum. In regular Drums mode, the drums change from song to song so one song a trigger might map to the hi-hat and on another song that same trigger might map to a tom. It will seriously throw you off. In Pro Drums mode, triggers will sound consistent and you'll be able to play by ear after learning the songs.
There is a game mode that allows you to free play the drums, which is handy for configuring the Zendrum.
Also there is a calibration wizard that adjusts for sound and video latency, I definitely recommend you use it after setting up the triggers on the Zendrum.
Learn Your Instrument mode is also handy for getting the hang of their wacky notation system. For example, the yellow line is used for both hi hat and high tom depending on the symbol that appears on the line.
Based on my testing it appears that Rock Band requires velocity values of 127 to trigger so I recommend setting up a program on your Zendrum with a Response Curve of 7 which outputs full velocity no matter how hard you hit the trigger. It seems Rock Band does not appreciate subtlety.
The MIDI Adapter has a switch on it with three positions: D K and G for drums, keyboard, and guitar respectively. I have used my Clavia Nord Modular G2 with the MIDI Adapter and the only thing I noticed was that the octave up and down buttons have no affect on the MIDI notes sent. Other than that it works without any configuration.
Finally, have a look at the marketplace to find new songs. There's a ton there and they're adding new songs every week. Each song tells you which instruments it supports and what difficulties. I noticed they recently put up the entire London Calling album by The Clash, so there's definitely some stuff worth checking out.