Wash the zucchini and pat dry with a clean towel. Trim off the ends, and cut each zucchini in half lengthwise. Scoop out any large seeds from the middle. Then use a julienne peeler, spiralizer, or just a knife to cut the zucchini into long thin strands or julienne it.
In a bowl, sprinkle the salt over the zucchini, and toss it well. Let it stand for 20 minutes on the counter.
Make the dressing by combining the sugar, Sichuan peppercorn powder, sesame oil, light soy sauce, lemon juice and rice vinegar. Stir until the sugar is completely dissolved.
After 20 minutes, discard the liquid at the bottom of the bowl of zucchini, and gently squeeze out some of the liquid from the zucchini.
Right before serving, mix the zucchini with the prepared dressing, garlic and chili oil if using. Garnish with sesame seeds, and serve immediately.