It can take anywhere from 2 hours to over 24 hours to hatch after pipping. It's hard work to break through that shell, and a chick needs to rest before attempting to zip. The blood vessels don't begin to recede until after that first pip, and the yolk needs to finish absorbing. All of that takes time.
If the chick is attempting to zip, but isn't making any progress after 2 hours, then you can try to start assisting. But you need to be very careful, and go slowly. And stop if there is any bleeding.
Gotcha. I'll see how far he gets in a few hours. Thanks!