Spray loaf pan with vegetable pan spray. In large bowl, mix flour, baking powder and salt together; set aside. In a mixing bowl, beat butter and sugar on low speed until light and fluffy. Add eggs one at a time, mixing until fully incorporated in between each egg. Add half of flour mixture, mixing on low speed until nearly combined. Mix in milk; add remaining flour mixture and beat until nearly combined. Add zucchini, carrot, and orange zest; beat until just combined. Smooth batter in pan.