I found that with the new Official Pi Zero case the HDMI to mini HDMI adapters wouldn't reliably stay plugged into the Pi Zero W.
The adapters are from the Pi Hut UK and Pimoroni UK.
I looked at a copy of the HDMI mechanical specification and the length of the Mini HDMI plug body does not seem to be specified.
So to get a reliable HDMI connection to the Zero W I got my razor saw and file out and took 1.5mm off the plastic at the plug end of the adapter. No metal shielding was exposed.