Place a deep heavy skillet on the stove over medium heat - I like to use my cast iron pan. Add the oil - about 3-inches - and bring up to temperature - about 350-degrees.
While you wait for the oil to heat up, beat together the egg and milk into a large bowl.
In another bowl, mix together the cornmeal, flour, onion powder, zucchini and cheese. Add the beaten egg mixture and stir gently. Let the mixture sit about 5 minutes before frying.
Meanwhile, line a plate with paper towels.
Using a small cookie scoop or melon baller, drop about 1-inch balls into the hot oil. Take care not to splash, and be sure not to crowd the pan or the hushpuppies won't crisp up.
Fry the hushpuppies until golden brown on one side - about 3-5 minutes - before turning. Once golden all the way around, remove to the paper-towel lined plate and sprinkle immediately with kosher salt. Serve hot.