Grease 9-inch pie dish. In skillet, melt 3 tbsp. butter over medium-high; add zucchini. Cook, stirring, 3 minutes; drain in colander. In bowl, season remaining ingredients; whisk to combine. Spread half of zucchini in dish; top with egg mixture and remaining zucchini. Bake at 425 degrees until set, 20 to 25 minutes. Let cool slightly.