You could either use the on-board audio out of the MacBook (with a y-cable - rca to mini jack, into one of the four audio inputs of the Prime 4) or connect an external audio interface in a similar way.
Also, I think you could plug the “Maschine MacBook” into the Prime 4 using the second audio interface and just select one of the 4 channels inside Maschine software as an audio out.
I don’t have the Prime 4 to confirm, but the latter should be the best solution.
Maybe @JWiLL can chime in to help?