The Z2's were built in 1994-95
A Z2 has one note map, instead of the current ZX @ 16.
It is the same body design as now, but doesn't have a MIDI IN port on the top.
It doesn't have a sustain jack or momentary switch, and requires a $450 total rebuild to bring to current specs from the original datawheel operating system and circuitboard. (It may still play great "as is" if all you need is a drum trigger for a drum sound module- Roland/Alesis, etc.)
Hope this helps!