Re: connecting second z-stepper-motor

Why don't you solder the two steppers together? Parallel connection would be the easiest, but series connection is better for the driver.

Parallel:
black to black
green to green
etc...

Series:
black1 to green2
green1 to driver_pin2

black2 to driver_pin1

blue1 to red2
red1 to driver_pin4

blue2 to driver_pin3