In a large bowl, stir together the bulgur and boiling water. Cover and let stand until the liquid is absorbed, about 30 minutes.
Meanwhile, grate 1 teaspoon peel and squeeze 1/4 cup juice from the lemons and set aside.
In a 12-inch nonstick skillet, heat the oil over medium-high heat until hot. Add the onions and cook until beginning to soften, 3 to 4 minutes. Add the tomatoes, squash and zucchini. Cook until the vegetables are tender, 6 to 8 minutes, stirring occasionally.
Stir the vegetables into the bulgur with the lemon peel and juice, mint, parsley, 1/2 teaspoon salt and 1/4 teaspoon pepper. Spoon the mixture into a container with a tight-fitting lid. It can be refrigerated up to 1 day.