In a bowl, cream the butter and brown sugar until light and fluffy, 5-7 minutes. Add the egg and mix well. Combine dry ingredients; add alternately with milk to creamed mixture. Stir in zucchini, walnuts, raisins and orange zest. Drop by teaspoonfuls 2 in. apart onto greased baking sheets. Bake at 350° for 12-14 minutes or until edges are lightly browned and cookies are set.