In a large bowl combine flour, sugar, brown sugar and salt. In a medium sized bowl combine eggs, vanilla, and 1 cup of chocolate sauce and butter. Fold wet mixture into dry mixture and combine completely. When all lumps have been removed fold the zucchini into the brownie mixture and stir well.
Pour batter into greased baking pan and set timer for 8 minutes. Remove brownies from the oven and drizzle the additional chocolate sauce over the top of the brownie batter. Use a knife to pull the sauce back and forth over the top of the brownie. Return brownies to the oven and bake for an additional 15 minutes.
Use a clean fork to test for doneness. Cut and enjoy!