User blog comment:IamJakuhoRaikoben/Chapter 450: Alone in all the World, Review./@comment-25111584-20150901154629/@comment-7418318-20150901202150

It took years to dispell Iced Shell and that spell was cast by a mere Human.

How many decades would they have to marinate in the moon-light to have a curse cast by a god dispelled?

On the other hands Zeref literally has all the time in the world, if he has enough patience.