Prepare the yogurt. Whisk together yogurt, lemon juice, and sugar in a small bowl to combine. Season with salt.
Rinse lentils, then soak in 2 cups of water at room temperature at least 1 hour and up to 12 hours (soaking lentils makes them tender and a lot easier to blend).
Meanwhile, trim ends from zucchini and cut crosswise into 3 pieces about 2" long. Cut each piece lengthwise into 1/4"-thick planks. Stack a few planks and slice lengthwise into 1/4"-thick matchsticks (about the size of a skinny french fry).
Transfer zucchini to a colander set in a medium bowl. Add onion and 1 tsp salt and toss to combine. Let sit until vegetables look wilted and softened and about 1 Tbsp liquid has released into bowl, 30 minutes to 2 hours. Gently pay dry with paper towels to remove any excess moisture.
Drain lentils and transfer to a food processor. Add chile powder, turmeric, and 3/4 tsp salt. Pulse, scraping bowl sides, until a purée forms. Transfer to a medium bowl and add zucchini and onion, parsley, and lemon zest. Toss with a rubber spatula to combine.
Line a rimmed baking sheet with paper towels; set a wire rack inside. Heat ghee in a medium cast-iron skillet over medium-high until a pinch of batter added to pan sizzles and sputters.
Using a large spoon, scoop out about 1/4 cup batter, then use a second large spoon dipped in the hot ghee to carefully scrape into pan; flatten with ghee-coated spoon. Repeat for 3 more fritters. Fry until deep golden brown on the first side, about 3 minutes. Turn over with a wide slotted spatula and fry until deep golden brown underneath, about 3 minutes.
Transfer fritters to prepared rack to drain; season with salt. Repeat with remaining batter (you end up with 8-10 fritters total).
Transfer fritters to a platter and serve with lemony yogurt alongside.