1. In a large nonstick skillet over medium heat, sauté the garlic and onion in the olive oil until the onions begin to turn translucent, stirring constantly so the garlic doesn’t burn, about 3-4 minutes. Add the zucchini and squash, tossing well with the olive oil mixture. Sauté over medium heat for 3-4 minutes. Add the chopped tomatoes. Continue cooking and stirring until the zucchini and squash are tender and the tomatoes have broken down, about another 2 minutes.
2. Toss the hot mixture with the parmesan cheese. Serve immediately.