With regular chicks... I had a silkie hatch once very fast over a 1 hour period...from the time it peeped, shell cracked, until it totally came out of the shell.
But by far the fastest to hatch were the Coturnix Quail.... Literally, they were popping out ---like popcorn---as I sat there watching the incubator. I think 3 or 4 came out in the few minutes I sat there watching. It was incredible!
The first time I hatched I had humidity up like 70+ percent and they suddenly just popped out, I really rarely saw any of them do the routine pip, zip, hatch. I'd look at the bator and see nothing, come back half and hour later and see two more chicks!!! All wet. But that was also my worst hatch as I only hatched 12 out of 20 The last two hatches I've set humidity around 65% and I can see very clearly the hatching process and I hatched over 85% Good luck.