Battery power for Pi Zero 2 W + 7.3" e-ink display

I am doing this with an Inky Impression 7.3” and a Witty Pi L3v7 hat on a Zero 2W. The battery is a 6600mAh from Adafruit. This works great as long as you do the SPI speed fix noted at Inky Impression 13.3" + Witty Pi + Raspberry Pi Zero W2 not working