Ok he may just need time with not being able to finish the zip. He could also have development issues with not being able to finish hatching. For me time will tell and you have done all you can. Difficult hatches can just be worn out and tired.
Try not to worry about your eggs. I open mine with pips to remove fluffed up chicks when it’s full with no ill affects.
Try not to worry about your eggs. I open mine with pips to remove fluffed up chicks when it’s full with no ill affects.