I had built [similar repository](https://github.com/computationalprivacy/unveil-pi-data-colle...) as a part of wifi data capture and visualisation experiment ([Project UNVEIL](https://github.com/computationalprivacy/unveil-deployment)) but it used external antenna.
Any links on how does underlying hardware work to enable simultaneous connections?
https://blog.thewalr.us/2017/09/26/raspberry-pi-zero-w-simul...
> At this point, we should be able to connect a device to our Raspberry Pi Zero W’s AP SSID, while we also have our RPi connect to another access point for internet access, and we should be able to access the internet from that device through our RPi.
The "simultaneous" aspect seems to be achieved by having two devices: wlan0 and ap0, the latter created by udev.