In Homer's "Odyssey," Zeus is a driving force behind most of the plot development. As the strongest of the gods, both other gods and mortal characters beseech Zeus so that desired events might take place.
The conflict of the Odyssey revolves around Odysseus, who is far from his homeland and wants to return, and Poseidon, who seeks to delay his return as long as possible. Poseidon is aware of Zeus' decree that Odysseus must indeed make it home safely, so he must ask Zeus whenever he wants to harm Odysseus.
Odysseus also prays to the gods, namely Athena, who beseeches Zeus on his behalf.
Zeus is not fully in control of every situation because he, like the rest of the characters in the Odyssey, is subject to the fates. The fates direct the major flow of events in the story and not even Zeus can oppose them.
Zeus also plays a crucial role in places where the Homeric narrative differs from the tradition of the Greek people. When Odysseus kills the suitors that have taken over his home, Greek tradition dictated that the families of the suitors would in turn kill Odysseus. At the end of the narrative, however, Homer invokes Zeus to supersede that tradition and keep Odysseus safe from what would otherwise be certain death.