Using second Pi Zero for second camera

I am only just getting started with OpenHD, but thinking ahead, just got my first connection between air (Pi Zero 2) and ground (Pi 3B+) working, but I am already thinking ahead about what I would like to do:

Is it possible to use a second Pi Zero for the second camera?

I know there are other options for second cameras, like USB cameras, but I want to build a mapping drone with one front-facing camera and one downward-facing camera that is taking & saving photos whenever it gets a certain signal from the flight controller. I want to be able to switch between the two cameras in my live video feed but the mapping should happen regardless of which video feed is transmitted by OpenHD.

So my preferred solution would be to have a second Pi Zero with a second camera where I run my custom code that handles the interrupt-driven photo collection, potentially some additional stuff (e.g. GPS tagging of photos), and when that Pi Zero isn’t busy taking a photo it somehow streams the video to the Pi Zero that’s running OpenHD. Apart from being able to use two Pi Cams, this has the advantage that I (hopefully) don’t need to worry too much about my code messing with the functioning of OpenHD.

My question is: How can I get a video feed from a second Pi Zero to the Pi Zero running OpenHD?
If this was a generic “getting bits & bytes from one Pi to another” issue I’d try to directly wire a UART serial connection. But I guess the video needs to get to the OpenHD air unit in a format that it understands. What’s the easiest way to do this?

Thank you very much for your input!