Prepare outdoor grill for direct grilling over medium-high heat. Cook penne as label directs; reserve ½ cup cooking water. Drain penne; return to saucepot and cover.
In large skillet, toast sunflower seeds over medium-high heat 4 minutes or until lightly toasted and fragrant, stirring frequently; transfer to plate to cool.
Spray squash and zucchini with cooking spray; place on hot grill rack, cover and cook 5 minutes or until grill marks appear, turning once. Transfer squash and zucchini to cutting board; carefully cut into 1" pieces.
In same large skillet, heat oil over medium-high heat. Add tomatoes; cook 1 minute or until tender, stirring frequently. Add garlic; cook 30 seconds or until fragrant, stirring frequently. Add arugula, vinegar, lemon juice, salt, pepper, penne, reserved cooking water, squash and zucchini; cook 1 minute or until heated through, stirring occasionally. Serve penne mixture sprinkled with cheese and sunflower seeds. Makes about 8 cups.