In a large bowl, combine the zucchini, garlic, scallions, ricotta, eggs, lemon zest and 1 teaspoon each of salt and pepper. Stir well, then stir in the flour just until incorporated.
Line a large baking sheet with paper towels. In a large skillet, heat 1/4 inch of olive oil until shimmering. Working in batches, add 2-tablespoon mounds of the zucchini batter to the hot oil, spreading them to form 3-inch fritters. Fry over moderately high heat, turning once, until browned and crisp, about 3 minutes. Drain the fritters on the paper towels and serve right away, with lemon wedges.