Very big problem that Zoe and many other recent champs have that makes them OP is...
... retardedly low mana costs.
You can spam and spam and spam and spam, spam over 20 rotations without going oom. Back in the day even with Athene's you couldn't do more than a few rotations and then go oom. Now with manaflow band and last chapter you are basically manaless, congrats!!! Especially the broken abilities like Zoe E that used to cost 100+ mana on older champs. Even the spammable damage abilites like Orianna W or Lux E cost 100+ mana and this broken overloaded ability that has range from beyond vision range, has 2 forms of CC, guaranties death on squishies and 50% hp lost on tanks and has a low cooldown with a cooldown reduction integrated into it costs 80 at all levels. Even balanced champs with tons of counterplay like VelKoz feels annoying due to all his abilites costing 50 mana, let alone these overloaded ones...