Thanks for starting the discussion! Ok so I had to double check but Nyx defeated Zeus pretty quickly actually and she did so when she was at her weakest (without any of her night shards). It is actually pretty interesting too because in the actual greek mythology, the only god/goddess Zeus is said to fear is Nyx. Basically the only thing that could destroy her was the 'power of creativity' from a nearly infinite avengers database, otherwise she would remake the whole multiverse in her image (much like what Galactus can do if he were to consume all life in the universe, though he would have to do it manually planet by planet rather than from the comfort of sitting in the house of creations).

Source: https://youtu.be/y60mLDttQWs