Heat oven to 350 degrees F (175 degrees C). Grease and flour bottom only of a 9x5 inch loaf pan.
In large bowl, cream brown sugar and margarine until light and fluffy. Reserve 1 tablespoon pineapple juice. Stir in pineapple, zucchini, and eggs. Add flour, baking soda, cinnamon, salt, and allspice; blend well. Fold in nuts. Spread evenly in prepared pan.
Bake for 60 to 70 minutes, or until toothpick inserted in center comes out clean. Cool 10 minutes, and then remove from pan.
To Make Glaze: Combine confectioners' sugar, reserved pineapple juice, corn syrup and 1/4 teaspoon ground cinnamon. Mix until smooth, and spoon over warm loaf. Cool completely on wire rack. Wrap and store in refrigerator.