A ZVD (Zero Voltage Diode) is a circuit that behaves like an ideal diode (a diode with zero voltage drop).
Powering through the GPIO connector is not a strange thing. The pins marked 5V and GND are connected to the USB power input. ( look at the schematics )
If you don’t know what you’re doing, then you need a diode.
And if you need a diode, it must be a ZVD, because even the 0.6V voltage drop on a normal diode junction will render the rPI very unstable.
In the Zynthian I built, I used a similar connector on the rear case panel with a short cable from the connector terminals to a micro USB male connector.