Lewis & Short

Zēthus, i, m., = Ζῆθος, a son of Jupiter by Antiopa, and brother of Amphion, Cic. de Or. 2, 37, 155; id. Rep. 1, 18, 30; Auct. Her. 2, 27, 43; Hor. Ep. 1, 18, 42; Hyg. Fab. 76 and 155.