Input Type
Unless you have a totally customized Zendrum with a non-standard allotment of triggers and controls then there should be no reason for you to need to change the Trigger Type for any trigger on your Zendrum.
Trigger Types fall into two categories:
Peak Detectors
This is a control that watches for 'spikes' due to being struck. A MIDI message is sent out once for each spike (though in the case of Note ON/OFF, both the Note ON and Note OFF are both sent for each single strike). All the round triggers pads fall into the Peak Detector category. If you have a external trigger pad or kick pedal hooked to your Zendrum then it too is classified as being a Peak Detector.
Change Detectors
A Change Detector is a control that watches for variable changes in its input voltage. Examples of these are the sustain switch, any variable foot pedals (high hat, volume, etc) or any knobs. Change Detectors will send out their MIDI messages whenever a change is made to the control's position.
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Care should be taken to not assign the wrong Trigger Type to any given control. No damage will occur, however the triggers or your Zendrum may become unresponsive when played with incorrect Trigger Types.
ZenEdit will warn you if it sees an unusual Trigger Type assignment.