In a large bowl, combine the corn, onion, parsley, and zucchini and toss to mix.
Add the flour and toss with your hands, separating all the ingredients to be sure they are all coated evenly with the flour.
Add the salt, pepper, and sparkling water and mix all together. The mixture should be airy and light, but not wet; do not overmix.
In a large heavy saucepan or deepfryer, heat about 4 inches of vegetable oil to 375 degrees.
Gather the batter into loose, very freeform fritters about 3 inches in diameter (when you gather them together, compact just slightly to hold in a mass, but there will still be lots of stray bits of vegetable sticking out and some will fall off and separate from the main clump).
Deep fry them, 2 at a time, until they are golden brown, about 3 to 4 minutes, turning over halfway through. Stand back and watch out for splattering oil for the first minute or two.
Gently remove them to paper towels, drain and keep warm in a low oven while you finish cooking the other fritters.