The Pi Zero can be powered via its USB port, allowing you to power it and communicate with it over the same wire. One potentially useful application of this is the USB gadget, which makes the Zero act like any number of USB devices.
I wanted to take a USB A to USB MicroB cable and use it to connect a Pi 3 to a Pi Zero (via their USB ports). Regrettably, the Pi 3 does not provide sufficient power for the Zero, and the Zero just boot loops. This can be resolved by powering the Zero separately, which will impact my power design requirements later in this project.
According to RasPi.TV, the Pi Zero draws ~240 mA while taking video. I will need to power at least 4 of these simultaneously as well as a Pi 3, which seems to average about 300 mA in these tests. I’ll therefore need a portable power supply capable of delivering at least 1.3A across 5 USB ports for several hours. I have yet to find a power brick with that many connections, so I’ll probably need a powered USB hub.