Toss well to coat in the flavors and cook another 3 minutes. In a large skillet, saute zucchini, yellow squash, onion and garlic in olive oil until vegetables are … Heat the oil in a large skillet over medium heat. Add the zucchini and spaghetti squash to the skillet … Add garlic and saute until slightly yellow in color. Meanwhile, heat a large skillet over medium-high heat. Add the oil, pepper flakes, garlic, shallots and 1/2 teaspoon salt. Drain the zucchini and rinse with cool water. Add the zucchini and yellow squash and season with 1 teaspoon salt. Cook, stirring often, for 2 minutes. Add the shallots and garlic and saute for 2 minutes. HEAT olive oil in a large skillet over medium heat.