Combine flour, baking powder, soda and salt. Set aside. Cream butter and sugars; beat in eggs one at a time and vanilla. Stir in buttermilk alternately with flour mixture. Fold in apples, nuts and orange peel. Pour into two 8.5 x 4.5 x 7 cm greased and floured loaf pans. Bake at 350 degrees 50-60 minutes or until wooden pick inserted near center comes out clean. Cool in pan 10 minutes; remove from pan and cool completely on wire rack. Wrap and let stand overnight to allow flavors to blend.