First thing is to select the Midi channel on the Zendrum and set the same on your MAC program. Use the Zendrum display and control pad to browse to the MIDI channel (CH) setup. Once you are there it will show the MIDI channel which by default is 10 ( I think!). You can change it with the arrows on the control pad. Then go to your MAC software and set it up on the same channel.
But also make sure you have the routing of the MOTU correctly set, input to output. On clockworks you'll see all inputs and outputs in a graphical display where you can drag the mouse to connect them.
At this point all MIDI notes should be arriving to your MAC!