I need to test on hard. But on easy, I used mainly Nycto archers and Mitachurls to kill one Eye in one wave, the other Eye on the second wave. Then, I used a Mitachurl/Nyco Archer combo with Samachurl/Nycto Archer combo, split into two groups (one going mainly upwards, the other going mainly downwards, to split Venti’s focus. Kill the adds, then Venti.
Hard mode/Helichurl though; you might need to just wait Lawachurl/Megachurl/Rogue. You could potentially use heroines, but good ones won’t be that accessible. You can utilize Mona to do cheese strats, Noelle for thicc shield, Keqing for crazy AOE.