I apologize if I'm looking at this wrong way, but it seems rather simple from my understanding.
Code:
Servos[1-4].set(joystick.getDirectionDegrees());
Motors[1-4].set(joystick.getMagnitude+/-joystick.getTwist());
Of course you'll need to do some adjusting for the servos and a the twist, but I think that's all that needs to be done.