In large pot of boiling salted water, cook pasta according to package instructions. Reserve 1/3 cup pasta-cooking water; set aside. Drain pasta.
Meanwhile, in large high-sided skillet, heat 1 tablespoon oil over medium-high heat. Add prosciutto; cook 2 to 3 minutes or until crisp, stirring frequently. Transfer to small bowl.
Add remaining 1 tablespoon oil, garlic and zucchini to skillet. Cook 2 to 3 minutes or until zucchini is lightly browned, stirring frequently. Add walnuts; cook 1 minute, stirring constantly.
Add cheese, lemon juice, pepper and pasta-cooking water to skillet. Cook 3 to 4 minutes or until slightly thickened. Add arugula, pasta and prosciutto; cook 1 minute or until heated through.