Designed with a Pi Zero 2 W, but should fit the other zero models.
Link to Waveshare adapter: Raspberry Pi Zero To 3B Adapter, Alternative Solution for Raspberry Pi 3 Model B/B+ | Zero-to-Pi3-Adapter (A) (waveshare.com)
Hardware: 4 M2.5 screws (6 mm) and 4x M2.5 hex nuts.
The fit is quite snug by design. Fitting the adapter and pi in the case may require a bit of wiggling it around.
The author remixed this model.
Took heavy inspiration from the design of this model.
Screw placement is for a Pi Zero to 3B adapter.
I/O cutouts were modified to account for differences between the pi 5 and the pi 3 adapter.
Two additional standoffs with guiding pegs added. Hole patterns changed to honeycombs. Side vents removed.
Dimensions for a snugger fit.
Added cutout for GPIO cable(s)