I have a similar-ish setup in the form of the ClusterHAT on a Pi 4 with 4x Pi Zero W connected to it. It gives me 4 individual Pi Zero machines (each with wireless) connected over the USB-Ethernet gadget interface to the Pi 4 which you can then bridge the interfaces as you need.

My purpose was to have a SFF of individual wireless clients that I could control over SSH to do some network testing. Added benefit, the whole thing can be powered from a single PSU into the Pi 4.