Preheat oven to 350°F. Bring a pot of salted water to a boil. Line a rimmed baking sheet with foil, and mist with cooking spray.
Mix turkey, zucchini, Triscuits, egg, pepper, half of scallions and half of garlic. Form into 30 1 1/2-inch meatballs; place on sheet. Bake 20 minutes.
Warm oil in a 12-inch skillet over medium heat; sauté remaining scallions and garlic for 1 minute. Stir in tomatoes and bring to a boil. Reduce heat and simmer, stirring often, until sauce thickens, 8 minutes. Stir in meatballs. Reduce heat to low.
Add spaghetti to boiling water and cook until al dente, about 8 minutes. Drain; top with meatballs, sauce and Parmesan, and serve.
