I am running on a zero as well, the only different equipment I am running is the Adafruit Motor controller hat, but that should just be a PCA9685 as far as the pi knows.Now isn't that interesting, no memory increase and behaving like its supposed to. Looks like your running a mix of 2.0 and 2.1 versions. The one thing that jumps out at me is that you are running on all zero's, not sure the versions should make a difference but I need to go and look back at ryan115 and see what hardware he is using but that is a difference.
@Ranjib is the pico running a PCA9685 for pwm, or running off of the pi directly? Same on the nano?