[Scaevolus]

Woops, forgot the major issue-- the Pi Zero only has one USB port (the other is just for power), so you couldn't get video frames in at the same time as you pretended to be a keyboard.

[mtlynch]

The Pi Zero's power port is actually a USB OTG port. I used it in my precursor project to forward keystrokes:

https://mtlynch.io/key-mime-pi/

[magicalhippo]

On the web page you explicitly say to connect it to the port labelled "USB", which is not the power port.

[mtlynch]

Whoops, you're right. I misremembered. It's power on the Pi 4 and data on the Pi Zero.

Thanks for the correction!