This description is specific to the Quad-head version of the Zx0Q. At the time of writing this is the only model of the Zx0Q I have seen. I assume it will be similar or easier for others in the range.
The first step is fairly straightforward: You need to remove the foot, two screws on the back panel, and the two screws towards the rear of the unit - one on the top and one on the bottom. After that the side cover can be slid back and removed.
I assume that's it if you've got a basic Zx0Q. However in my case I was greeted with:
The front panel is to the left, the RAM sockets are under what appears to be a SSD carrier and the SATA SSD can't be seen as it is under the daughter board that carries the additional two video ports (top right). This video daughter board is secured by two screws by the rear panel and the other end of it rests on two tabs on the side of the metalwork of the SSD carrier.
If you undo the four screws that hold the metal SSD carrier in place you'll find that you can't remove it thanks to the presence of the video daughter board - you need to remove that first.
Originally I wiggled the daughter board around and managed to get it out of the way without disconnecting it. This was an error as I eventually ended up half pulling out the connecting ribbon cable from the motherboard and, in the process of replacing it, slightly damaged the plastic latch that holds it in place. I strongly recommend that you disconnect the end connected to the daughter board (highlighted below) along with the power connection:
The ribbon cable has a bit of black tape each end to help keep it in place. In the photo this piece of tape has been removed. At this end of the ribbon cable the connector is a standard ZIF arrangement where you flick the black bar up to release the trapped cable.
With the additional display board out of the way you can then remove the metalwork of the SSD carrier and so gain full access to the motherboard:
