Mix together brown sugar, oil, eggs, lemon peel and juice until well combined. Add flour, soda, salt, zucchini and nuts; stir just until combined. Spread evenly in ungreased 10 x 6 micro-safe baking dish. Microwave (med-high 70%, uncovered, 7 minutes, rotating dish once. Then, microwave (high) 2 1/2 to 3 1/2 min or until no longer dought, rotating dish once. Cool completely. Combine powdered sugar and margarine in micro-safe bowl. Microwave (high), uncovered 15-20 seconds or until margarine is softened. Blend in lemon juice and enough water until of spreading consistency. Spread over bars. Cut into squares.