Zeus was the King of the Gods and the oak tree was known to be the King of Trees thats why it's associated with the almighty Zeus
The Aetos Dios was a giant, golden eagle which served as Zeus's personal messenger and animal companion. That's why The Eagle was one of Zeus's symbols.
Zeus: God/Goddess Annotated Project
By:Rawan Abusnaina
As a token of reward from when Zeus freed the cyclops. He was given a lightning bolt. Which is the strongest symbol associated with Zeus. Zeus used the bolt in many battles including his famous battle with his father, Cronus.