A theory that will start to show up in books coming out fairly soon is that the Titans were Magic, and the Olympians were Faerie. The Titanomachy was a war in which one Realm pushed the other off its position of supremacy.
The Titans work very well as beings of Magic; they are concerned with the vast forces of the universe, and don't have a deep interest in humans. The Olympians, on the other hand, are constantly meddling in the affairs of mortals, which is a much more Faerie trait in ArM5.
So, I'd say that Zeus is just a big Faerie.