So one more thing here …
I pulled out my 90s equipment … a creative FPS 2000 surround sound thing. Which is a subwoofer and 4 satellite speakers connected to the subwoofer.
The subwoofer has 2 inputs:
My Zen Can has a balanced 4,4 pentaconn output. (I’m keeping the unbalanced 6,3 for the headphones).
How the hell do I connect that? 
Since the zen can has only a balanced output and the sub has 2 mono 3.5 jack input you should connect directly your DAC to the sub with an RCA to jack 3.5 mono and eventually buy an RCA splitter. So you connect the DAC to the input of the spitter/selector an output of the spitter to the zen DAC and an other to the sub and select what you are using each time
Thanks @lafonte!
the sub has 2 mono 3.5 jack input
Actually I think these are 2 stereo inputs since each drives 2 speakers. So one jack is front left / right, one jack is rear left / right.
Does that make any difference to what you proposed?
In that case you need a 4 channels dac, or connect the sub to the dac with an rca to stereo 3.5 jack but you will get a stereo system with 2 speakers for channel and a sub. The spitter will work but just using the system in stereo
edit: drive 2 amplifiers with a single signal can cause problems, so probably connect the mono signal to the stereo input of the sub can be a solution that is less than optimal. better check the manual of the system first.
Right I figuered … I think I’ll simply stick to 2 speakers for now instead of the 4.
Thanks!