In a small bowl whisk together the sugar, the salt, the lemon juice, and the oil. Transfer the vinaigrette to a skillet, bring it to a boil, and add the zucchini, stirring to coat it with the dressing. Simmer the zucchini for 3 minutes, or until it is crisp-tender, stir in the mint, and let the zucchini cool in the dressing. Serve the zucchini at room temperature.
