Beat together eggs, oil, sugar and vanilla. Sift together flour, baking soda, salt and baking powder. Mix into egg mixture. Blend in dates or raisins, zucchini and nuts. Place into greased and floured 15x10x1" jelly roll pan. Bake at 350 degrees for about 30 minutes. Icing: Beat cream cheese until fluffy. Blend in sugar, vanilla and milk. Add a little more milk if necessary to reach spreading consistency. Spread over cooled bars.