For those of us who were playing or watching during Season 3, these picks may not be much of a surprise. Zeus and Thoth were both stellar mid lane picks throughout the recently finished ranked season -- and while their job of "obliterate literally everything in front of you" was headlined by Scylla, recent changes to the way Conquest works leave these two mages (with slightly better wave clear and early fighting potential) in a much better spot than the tiny terror of the deep.
While Zeus is still the same god of lightning bolts and absurd damage he was last season, that's fine. Being able to single-handedly annihilate an enemy squad if properly guarded is good enough to keep the God of the Sky among the top picks for the middle lane (even when he's built a little tanky).
Thoth was already fairly well positioned headed into Season 4. His kit promoted extremely safe laning, he had powerful poke damage to soften up an enemy lineup, and late game his ult could simply delete anything less durable than a warrior. Really, he had everything you could ask for out of a competitive mid laner...
...and then they gave him a stun. While it only lasts a single second, upgrading the Crowd Control on an already prominent Mage like Thoth is a *huge* boon to any allied Junglers or rotating Supports, and vastly increases the lethality of any ganks his team wants to lend a hand with.
Early clear, powerful contributions to teamfights, and high single-target lethality mean Zeus and Thoth are grade A picks going into Season 4. They'll be powerful additions to any serious mid laner's arsenal.