run your op-z audio outs into OP-1. go to the tape page and hit the mic button so the audio is passing through. select an effect within the tape FX to alter the op-z audio.
now go back to either the synth page or the drum page and jam on top of the op-z or use the op-1 sequencers and jam on the 'z.
vocal samples on the OP-1 are really fun.
(my session was Lyra-8 into OP-1 into Heat into Ableton)
Adjust the overall EQ level, paying attention to the distortion - the OP-1 EQ is very musical and good for richer sounds, specially in the Mid frequencies;
Increase the Master Out, adjusting the Drive and Release.
With this basic setup adjusted, you can do some 4-track tape magic! Although the overdubs degrades the sounds (like the original 4trax dubs! :), with time you will learn where it cuts and with the right EQ and fine tunning you can fatten a lot the sounds. I really like to do some radical EQ + FX + drive, tape record the track and record it again activating the track internal mic.
Finally, as told by @KOHLBERG, the OP-1 reverb (even with gentle settings) can do an amazing work opening the sounds. I also like a discrete CWO to add some movement.
And before I forget: although “cutting your dubplate” is very practical, it´s always better to record your beat from the master output, processing through an analog mixing board. Even cheap mixers can add some instant mojo with a little gain + EQ + compressor knob (which is an industry standard nowdays).