I found the Zapp spec sheet here
SY42STH47-1684B.pdf
It shows that BLK and GRN are one coil, and RED and BLU are the other. So hook one coil to 2B and 2A, and the other coil to 1A and 1B. If it doesn't work, just swap the wires of one of the coils (like RED and BLU).
When you've gotten it to work, let us know the correct order and maybe update the wiki.
Going about it another way, the
Stepperworld Bipolar Tutorial has a section called
Shortcut for finding the proper wiring sequence
Quote
Connect the 4 coil wires to the controller in any pattern. If it doesn't work at first, you only need try these 2 swaps...
1 2 4 8 - (arbitrary first wiring order)
1 2 8 4 - switch end pair
1 8 2 4 - switch middle pair
You're finished when the motor turns smoothly in either direction.
This shows you how to wire ANY 4-wire stepper, even if you don't know the wiring at all. Also, how to wire a 6-wire unipolar stepper to run as a bipolar stepper in either high speed or high torque mode.
The tutorial also tells you how to figure out the wiring of a stepper with a good ohm meter. Highly recommended!