Looking to piggyback a pi on top of an arduino robot. How to power it?

Question

I recently bought and assembled this Arduino-based robot turtle kit, and it's fun but I find microcontroller code a bit limiting, and I'd like to stick a raspberry pi on top of it to provide some brain power (and program it in a language other than C).

It seems like a Pi Zero W would fit the bill perfectly, and I'm reasonably confident I can connect to the Arduino over USB from it, but I'm a little baffled as to how I might power it and am looking for some advice.

The robot is currently powered by 2 18650 batteries, which plug into a servo control board; the Arduino Nano microcontroller plugs directly into this board. I know next to nothing about electronics, but SunFounder did helpfully provide a circuit diagram, clipped from the PDF below:

All I can really tell from that is that it uses 5V power, which I understand is not compatible with Raspberry Pis (or is that only for logic)?

Anyways, I'm looking for advice. My ideal solution would be to power both the Pi and the Arduino from the servo board, but I'm not even sure whether that's possible, advisable, or what sort of equipment I would need in order to do it.

Oh, just for completeness here is the circuit diagram for the MCU on the servo board as well (these are the stacks that the Nano plugs in to):

Answer 1

You can power the Pi from 5V, indeed that is NORMAL.

Assuming your power unit can actually supply the current required, the simplest solution is to power through the 5V, Gnd pins on the expansion header.

See Raspberry Pi Power Limitations

Actually interfacing is another issue, but you have not indicated what you intend. USB would seem an unusual option. I routinely interface Pi & Arduino, either directly using GPIO (level converters REQUIRED), serial, SPI or even I²C.