Heat the olive oil in a skillet over medium heat; cook and stir the onion until translucent, about 5 minutes. Stir in the sugar, then add the chopped zucchini, dill, and rice. Cook and stir until the zucchini is softened, about 5 minutes. Pour in the water, sprinkle with salt and pepper, and bring the mixture to a boil. Reduce the heat and simmer the mixture until the rice is cooked, about 20 minutes. Turn off the heat, and let the mixture cool to lukewarm.
Make a sauce by mixing the yogurt, garlic, and salt in a bowl. Serve over the lukewarm zucchini and rice.
