Preheat oven to 350 and spray a 9x13 baking pan with cooking spray.
In a large bowl, mix together the applesauce, sugar, syrup and vanilla.
Combine the flour, cocoa, baking soda, and salt - stir into wet ingredients (it will look pretty dry at this point - don't worry, it moistens up with the zucchini. However, if necessary, add a little more applesauce).
Stir in zucchini - if batter is still too dry, add a couple tbs of applesauce.
Add any optional ingredients (walnuts, chocolate chips).
Spread into baking pan. Bake for 25 to 30 minutes in the preheated oven, until brownies spring back when gently touched.