Preheat broiler. In a large bowl, whisk eggs, egg whites, 1/4 cup cheese, sage, salt and pepper until blended.
In a 10-in. broiler-safe skillet coated with cooking spray, heat oil over medium-high heat. Add zucchini and green onions; cook and stir 2 minutes. Reduce heat to medium-low. Pour in egg mixture. Cook, covered, 4-7 minutes or until eggs are nearly set.
Uncover; top with tomatoes and remaining cheese. Broil 3-4 in. from heat 2-3 minutes or until eggs are completely set. Let stand 5 minutes. Cut into wedges.
Health Tip: Using six egg whites, which is equivalent to three whole eggs, saves almost 30 calories and 4 grams fat per serving.