Ok, I think I know what pipping and zipping are, but I want to be sure. Could someone hand me the BYC dictionary?
So pipping is when the chick makes a hole through the shell, zipping is when the chick chips away at the shell in a circle (turning itself in the egg as it chips away). Internal pip is when the chick makes a hole in the membrane without breaking the shell, but you can hear the bird chirping inside.
https://www.backyardchickens.com/t/241913/dh-ds-dd-d-what-do-all-these-different-ds-stand-for