Whisk flour, sugar, baking powder, cumin, salt, and pepper together in a large bowl.
Whisk milk, melted butter, and eggs, together in a small bowl; pour into flour mixture and whisk to combine. Stir in zucchini, corn, and Cheddar until well combined.
Heat oil in a deep fryer or large saucepan to 350 degrees F (175 degrees C). Working in batches, drop tablespoonfuls of batter into hot oil. Fry until crisp and brown, about 4 minutes per batch, turning halfway through with tongs. Drain on a paper towel-lined plate.