Position oven racks to divide oven into thirds. Heat oven to 425ºF. Line two 15 x 10 x 1/2-in. baking pans with nonstick foil. Halve tomatoes; place tomatoes, 3 Tbsp oil and the garlic in a 13 x 9-in. baking dish. Halve spaghetti squash lengthwise and scoop out seeds. Brush cut surface of squash with a little of the remaining 1 Tbsp oil; place flesh-side down on a foil-lined pan. Quarter zucchini lengthwise and cut into 3/4-in. pieces. Place on other foil-lined pan; toss with remaining oil. Roast tomatoes and spaghetti squash on top rack 40 minutes until you can easily pierce squash shell. Roast zucchini on bottom rack 30 minutes, tossing once, until tender and slightly browned. Scrape strands of spaghetti squash into a large bowl. Toss zucchini with roasted tomatoes, the salt and pepper; spoon over spaghetti squash. Sprinkle with Parmesan, if using.