In one bowl, stir the dry ingredients together. In another bowl, mix the sugars with the margarine and vanilla extract until well combined, then stir in shredded zucchini (if your zucchini produces a lot of moisture after being shredded, squeeze out and discard some of the juice), walnuts and chocolate chips. Pour wet mixture into dry mixture and mix until just combined.
Grease a 5 by 7 inch rectangular baking dish and pour the batter into it. Bake at 350F for about 30-40 minutes. Cut and let cool a dozen minutes before eating and taking out of baking dish. Store uneaten portions in fridge.