Cook pasta in boiling water for 5 minutes, omitting salt and fat; drain.
Remove casings from sausage. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add sausage to pan; cook until browned, stirring to crumble. Remove from pan. Heat oil in pan. Add zucchini, onion, salt, pepper, and garlic. Cook 10 minutes or until vegetables are tender and zucchini begins to brown, stirring occasionally.
Combine broth and flour in a small bowl, stirring with a whisk. Add broth mixture to pan; cook 1 minute. Combine zucchini mixture, pasta, sausage, and feta cheese in a large bowl; toss well.
Spoon pasta mixture into an 11x7" baking dish coated with cooking spray. Sprinkle evenly with mozzarella.
Bake at 400 for 20 minutes, or until bubbly and lightly browned.