And at some point in the alternate timeline, they have to stop Zelena. Otherwise, it is an endless loop of curses back and forth, Groundhog Day-style. Someone has to have the wits about them, the memory required, to do what it takes to prevent the cycle from starting yet again. And in that case, why can they (assume: Emma) not stop Zelena before ANY of this happened, thereby avoiding Neal’s death altogether?
Yes, that’s my theory for what will ultimately happen, they’ll go back to the point in time when they landed in FTL at the start of 312, and this time defeat Zelena straight up, to avoid all the havoc she was responsible for setting in motion.