Housing for the ZERO-DISP-7A touchscreen from Waveshare
I tried to make it as compact as possible and to keep it as simple as possible.

Total height is about 25mm
Recesses for display control buttons on the side.
There are 2 slotted holes on the back for hanging it on the wall.
Cable feed for the power supply is possible from the side or from below.

Additional Parts:

4x Heated inserts M2x4mm

4x M2x8mm Screws (outer)

4x M2.5x8mm Screws (inner) 

Insert the threaded inserts into the “Front”-part from behind (without the Display installed). Be sure to not stick them through, so they won't contact the glass of the display from behind. There's very small distance between the inserts and the display glass.

Peel the foil from the adhesive on the backside of the displayy and install it into the “Front”-part. 

Now you can install your Pi Zero onto the Display and close the case with the “Back”-part.

Use M2x8mm (Not longer, or you will screw into the glass and potentially damage the display) for the outer 4 screws.

M2.5x8mm for the inner 4 to screw the backside onto the Display