142,983 km in diameter, approximately.
I guess you mean Jupiter.
There is no planet named after the Greek god Zeus. However, Zeus's roman form is Jupiter, the fifth planet from the sun.
Zeus Zeus
In Greek Mythology, Cronus was the father of Zeus. In Roman mythology Cronus was identified with Saturn.
The planet with a diameter closest to this value is Uranus, which has a diameter of 31,763 miles.
There is no proof that Zeus exist. I do agree with the first answer that there is no proof that he exists but in Roman times Zeus was Jupiter. (he was not named after the planet, the planet was named after him.)
The planet Uranus.
Zeus
Jupiter
the Jupiter diameter is 142,984km
It wasn't the planet Jupiter was named after the great Zeus
Mercury is the smallest planet, so there isn't one with half the diameter.
The largest planet in the solar system is Jupiter, with a diameter 11.209 times that of the Earth