Cook fettuccine as directed on package. Drain.
Meanwhile, in 12-inch nonstick skillet, cook onion over medium heat for 2 to 3 minutes or until crisp-tender, stirring frequently. Add zucchini; cook and stir 2 minutes. Stir in tomatoes and meatballs; cook 3 to 5 minutes or until thoroughly heated, stirring occasionally.
Add cooked fettuccine and pesto; cook and stir just until thoroughly heated.