[Gameplay] Zyra's plants get one shot by Corki's auto attacks(AA)

I was playing a game earlier today as mid Zyra against mid Corki and he destroys her plants in one auto attack(AA). I was discussing this with my friend and we came to the conclusion that it's because Corki's AAs deal magic and physical damage at the same time. Was this intended or is this an actual bug? I originally posted this in another board and was told to try and report it by a commenter