The Incan civilization flourished around 1500 Ad, nearly 2000 years after the height of classical Greek civilization.
When Hercules and Maytha first meet, Maytha says how he never saw a white man before, and Hercules remarks about how the Incans are a people he's never heard of before. Despite both of them being totally ignorant of each other's cultures, they speak the same language and have no trouble communicating this to each other.