If you intervene too early with an egg in an incubator, and it bleeds a little, you can stop and put the egg back for a while. But when the egg is under a hen, she might peck at the blood and hurt the chick.
So if you know it is no later than day 21, and might possibly be earlier, I would not intervene at this time.
I'm not good at interpreting candling photos, so I can't help there. But I thought zipping (going all the way around) was through the shell too, not just the membrane, and would come after an external pip