Bring 2 1/2 quarts of water to a rolling boil. Add 1 tablespoon salt, stir and put in the zucchini. Boil rapidly for 3 to 4 minutes, or until the zucchini are just done. Drain and leave to cool. Put the yogurt in a bowl and beat lightly with a fork until smooth. Add remaining salt, cayenne, roasted cumin, and sugar. Stir to mix. Heat the oil in a very small pan or skillet over fairly high heat. When very hot, add the mustard seeds. As soon as the mustard seeds begin to pop, this takes just a few seconds, pour the seeds and oil over the yogurt. Stir to mix. Gently fold the zucchini into the yogurt. Serve warm or cold.;
Note 1: Ground roasted cumin seeds, place 3 to 4 tablespoons of whole cumin seeds into a heated, small cast iron skillet. Keep over medium heat. Stir the cumin until it is a few shades darker and emits a distinct roasted aroma. Grind in a clean and dry coffee grinder and store in a tightly lidded jar.
Note 2: Garam masala, combine in a clean and dry coffee grinder 1 tablespoon cardamon seeds, 1 teaspoon whole cloves, 1 teaspoon whole black peppercorns, 1 teaspoon whole black cumin seeds, 1 2-inch stick of cinnamon, 1/3 of a whole nutmeg, and a curl of mace. Grind until you have a fine powder. Store in a tightly lidded jar.
Note 3: Rai masala, toast and grind 2 tablespoons whole coriander seeds, 1 teaspoon whole cumin seeds, 1 teaspoon whole fenugreek seeds, 1 teaspoon whole brown mustard seeds, 1 teaspoon whole peppercorns, 1 to 2 dried, hot, red chilies, and 5 whole cloves, using the same method as roasted cumin seeds.