There is a difference between power and strength. Hulk is the strongest avengers but Thor is easily the most powerful and he was powered way down in Avengers to make everyone else look good. Its similar to what happens to Superman on occasion in JL comics.
The reason why Zeus was able to kick Hulk's ass was due to the massive difference in power, Zeus is equal to Odin in power, who is the most powerful being in the 9 realms.
And Hulk has no chance against Odin-force Thor, who has the same power as Odin. Odin shakes the whole universe during some of his battles.