1. Cook pasta according to package directions in salted water; reserve 1/4 cup pasta water. Drain pasta and return to pot.
2. While pasta cooks, heat oil in a large skillet over medium-high heat. Add zucchini; cook, tossing occasionally, until browned and crisp-tender (5-8 minutes). Add crushed red pepper, marinara, and reserved pasta water; simmer, partially covered, until pasta sauce is thick (about 5 minutes). Toss pasta with sauce and divide among 4 bowls.