1Preheat the oven to 375 degrees F (190 degrees C).
2Heat butter in a skillet over medium heat; cook and stir zucchini and onion until tender, about 10 minutes. Add salt, pepper, garlic powder, basil, and oregano; stir to coat.
3Whisk eggs and mozzarella cheese together in a bowl. Stir zucchini mixture into egg mixture.
4Separate crescent dough into two rectangles and place into a 8x12-inch baking dish; press into bottom and slightly up sides of dish to form a crust. Spread mustard onto crust. Pour zucchini-egg mixture into crust.
5Bake in the preheated oven until set in the middle and lightly browned, 18 to 20 minutes. Cool before cutting into squares or wedges.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.