Returning to Zendikar isn't even hard.
Zendikar Resurgent, remember? One continent got pwned , but I'm pretty sure it will be treated in general of "And the eldrazi were defeated, everyone had a good time, and nothing of value was lost and not restored" because that's the kind of ending we got to the Battle For Zendikar.
Amonkhet is a little harder. Even then, they've dedicated themselves to planting the seeds in HoD, of those who will make the desert bloom and those who will go far seeking lands pure of the touch of Bolas. Now if someone was really cut loose this could be
absolutley fascinating. We see in HoD some of the varied reactions to the Hours that the orphaned and abandoned youths of Naktamun take, whether they remain faithful to the God Pharaoh in spite of the madness and destruction, succumb to despair, or enter violent dissent. It could be really interesting to see the effectively post-apocalyptic society ten years down the road (or even less) when the dust has settled a little and the survivors have formed their own factions. To see how they've adapted to being taken from a life of endless training for warfare alone and thrust into a life where rather than being provided luxury by the anointed they're forced to scratch their own living from a world that doesn't cooperate. Honestly that's part of why I'm sad that Hazoret lives: she gives a nucleus to build a new cultural monolith around, which is FAR less interesting than exploring diaspora and division. A world where the people of Amonkhet have a new (well, renewed at least) god to raise up and to protect them is less interesting than a world where the people must face freedom (horrible, horrible freedom?) and all the burdens
and opportunities that come with it.