Complex sentence: In classical mythology, Io was a beautiful priestess of Hera (Juno) lusted after by Zeus (Jupiter), who changed her into a heifer to deceive the goddess and have his way with her.
Split into simpler sentences: In classical mythology, Io was a beautiful priestess of Hera (Juno) lusted after by Zeus (Jupiter). He changed Io into a heifer to deceive the goddess and have his way with her.