You can remove a bit more following the zip line. I would remove to the right of th beak if you are looking at the photo. If the membrane is getting dry (turns yellowish brown) you can put some bacitracin ointment on it. If you do not have that, others use coconut oil, though I have not.Chick is turning but not cracking. I’ve removed some of the egg. Her beak is under that darker area on the left. Should I keep going?
If you see any active veining, stop. it is also best to leave the last bit for the chick to push out if possible. They need to do this to unfurl their feet and strengthen leg muscles.