Yes, I'm convinced it is zipping. I janked it out, pealed away some of the shell and put it back. Humidity is rather high in the incubator, so hopefully will not dry out (if it doesn't progress soon, I'll do a proper assist). I only removed part of the outer shell, not any of the membrane, so you can see how much it has done by itselfIf it is a true zip, then I would assist as four hours is quite long for a zip and may indicate issues such as malpositioning or being stuck/shrink-wrapped - that judgement is up to you though.