Zeus was the king of a village in Kanto. Per the traditions of the village, a competition was held to find a new king: The person who possesses the crown at sundown will be crowned the new king. At the end of the day, Hank was holding the crown and thus named as the king.
Zeus was not seen much throughout the course of the episode and so little is known about him. However, he seems quite eccentric for thinking it would be acceptable to have an Aipom for a king.