TOSS zucchini and salt in a colander in a sink. Let stand for 10 min to drain. Squeeze firmly to remove as much water as possible. Transfer zucchini and carrots to a kitchen towel. Spread evenly and roll up to squeeze out any remaining liquid.
BEAT egg in a large bowl. Add zucchini, carrots, feta, mint, parsley, onions, garlic and pepper and stir to combine. Stir in flour and baking powder.
HEAT 2 tsp of the oil in a large non-stick frying pan over medium. Scoop scant ¼-cup portions of zucchini mixture onto pan and gently press down with the back of a spoon, making 2-in. circles. Cook fritters until golden, 2 to 3 min per side. Repeat with remaining oil and zucchini mixture.