Grate zucchini and carrot, using the shredding disk of a food processor. Place in a colander and toss with ½ teaspoon salt. Let stand 30 minutes.
In a small bowl, mix together sour cream, parsley, lemon zest, Sriracha sauce and ¼ teaspoon salt. Refrigerate.
Squeeze zucchini/carrot mixture in cheesecloth or strong paper towel to remove as much liquid as possible. Transfer to a medium bowl and stir in corn, egg, onions, bread crumbs, corn meal and ½ teaspoon salt.
Heat a large skillet to medium heat, and coat the bottom with oil (If the temperature is too high, the outside will get too brown before the inside is fully cooked.). Add ¼ cup of the mixture for each pancake, pressing lightly with the bottom of the measuring cup to flatten. Cook until golden, about 3-4 minutes on each side. Drain on a paper-towel-lined plate, and place in a warm oven until all pancakes are cooked. Serve with the sour cream sauce and tomato.