It is possible, though highly unlikely.
Normally, I would say no, but there might be some opposite fruit than ambrosia that can take them down, such as when Hercules was rendered powerless in the Disney movie. I realize that Hercules chose to be robbed of his power, but even that scenario leaves the door open or at least cracked for a small chance of death for even Zeus.
Edit: Asklepios god of doctors was killed by Zeus. They weren't completely immortal.
In Greek myth, Dionysus died to become a god. As a Greek god, he does not die.
Oceanus the Greek god did not die in myth.
Apollo is a Greek God, they are immortal. They do not die. Hence, Apollo has not died.
Charon was not a Greek god- he was Hades' ferryman down the river Styx. He did not die.
Not in Greek myth.
The Greek gods never die.
Poseidon did not, and will not die.
NO
Forgetfulness
Eros the Greek god of love did not die. Eros was considered in Greek mythology to be a immortal god.
Since Apollo is a god, he is immortal
Hermes is a Greek god and immortal. Hermes did not die.