1. preheat broiler
2. thread beef, zucchini, corn, and tomatoes alternately on 4 (12-inch) skewers, Sprinkle with cumin and salt. Spray lightly with nonstick spray
3. Broil 4 inches from heat, turning every 2 minutes until zucchini is tnder and beef is cooked as desired, about 10 minutes for medium rare.