That doesn't look like zipping, more like damage from the broody. BUT it has been 24 hours, so I'd say may be time to help. The chick is still moving and breathing, right?
I'd put it in an incubator, if you have one. If not, I've used a small heating pad in a shoebox, egg loosely covered with a damp towel, and a thermometer stuck in there to monitor temperature.
Is it moving its mouth in a chewing or yawning motion? If so, give it more time. It may still be absorbing the yolk.
If not...
Very carefully peel a strip of shell around the zip area. All the way. Then VERY CAREFULLY and VERY SLOWLY start peeling the membrane along the zipline. The very moment you see blood, STOP and lightly press a piece of paper towel on the vessel to stop bleeding. And wait some more.
If no bleeding.....
Finish peeling membrane around the zip, and if the chick is strong enough, it will kick its way out in a few minutes.
If not, it's probably stuck to the membrane, or shrink-wrapped......
Carefully remove the top of the eggshell, and start removing more shell and membrane until you can see the yolk sac. If no yolk remains, he should kick free of the shell. Congratulations!
If there is still yolk, STOP and give it more time while sitting in the bottom half of the shell.
