hmm that does look crusty... keep in mind that if we operate on this egg, the other remaining eggs might also need help (drying out due to opening) but since so few eggs are left, I think I would open it personally... get the bathroom super hot and high humidity, run the shower for 10ish minutes (I also have a space heater in the bathroom), get a warm wet cloth to wrap it in. sterile tweezers, hand sanitizer for yourself
I would moisten the area around the zip with antibiotic ointment (without pain reliever) OR you can also use warm water (sterile, boiled but not boiling hot) and a q-tip... to me it looks crusted on/stuck... so you need to moisten the exposed areas all around the shell. the AB ointment/neosporin will keep it moist for hours while it waits. the water can dry out over a few hours, so you might have to re-wet in that case.
depending on how long it's been since it started zipping, you might put it back and wait longer, or help it zip a little bit more..how far zipped around is it? when did the zip start?
here is the detailed information on intervention, good read:
https://www.backyardchickens.com/t/9316/intervention-helping-your-chicks-hatch