User blog comment:IamJakuhoRaikoben/Chapter 468: Memory of the Stars, Review./@comment-4999650-20160110003724/@comment-7418318-20160110104425

That's not being loyal to both, that's pretending to be loyal while in truth betraying Zeref, even if it's "only" a partial betrayal.

Remember that right now Zeref wants to kill all Humans, starting with the ones on Ishgar, so letting anyone of Fairy Tail survive is already disobeying orders and actively hiding someone is outright treason.