NickD
16
With the Zoom you can use standard 1/4" leads for the connections, though the R16 will also accept XLR on all inputs.
Probably best to follow the standard 2 channel, 2 lead stereo connection to two inputs on the Zoom, because of the effects - you could in theory use the outputs as two mono channels for separate processing, but if you’re using the A4’s internal FX that’s not going to work out well.
One caveat of the Zoom: you won’t get any dedicated mixer controls beyond the level faders and the gain knobs. So you won’t be doing any live mixer action like tweaking effects sends or EQ on the fly - you can do both those things on the Zoom, but only by navigating to the appropriate menu and using the jogwheel. It’s easy to do, but a dedicated mixer is far more flexible in this regard. But if you’re doing most of your processing on the A4 itself, that’s not so bad.
Also if you’re using the Zoom as a USB interface you can of course apply effects in your DAW (and assign the R16 faders as MIDI controllers).
With the MD and the A4 you could in theory use up all the Zoom inputs - stereo outs for both machines, and then the four individual outs for the MD. That’d give you a lot of processing flexibility while recording and afterwards