I have a NTE1774 motor driver:
I want to hook it up to my arduino and use it as a stepper driver but cant figure out what Vz 1 and Vz 2 do.
If anyone knows please tell me.
-Pete
That is such a bad data sheet. 
However my guess is that it is actually just a copy of the L293D, in which case the Vz connections will be the motor drive voltage.