I found the pi zero too underpowered, and also had the Lack enclosure, so I just smushed these together to add a raspberry 2/3 to my MK3. As a bonus I made a different lid to connect GPIO's if you are into that kind of thing.
It's this:
..plus this..
https://www.thingiverse.com/thing:943567
Use supports for the cover.
The author remixed this model.