Similar to Can I power a Pi through a 5V pin?, but I want to acquire the 5V power source from another Pi. The first Pi gets its power via micro USB, and then I want to use pins 2 and 6 from that to power the second Pi via its 2 and 6 pins.
The trouble is every time I complete the connection, all power is lost on the first Pi and it shuts off (and the second one never lights up AFAIK).
I have confirmed that I can power the second Pi via pins 2 and 6 with 3 AA batteries. And of course pins 2 and 6 is supposed to deliver 5V power to another device. So why then can't I chain them together in this way?
Strictly speaking, this are Pi Zero W's.