FOR THE CAKE: Preheat oven to 350 degrees. In a mixing bowl, whisk together flour, cocoa powder, baking soda, salt and cinnamon for 30 seconds, set aside.
In the bowl of an electric stand mixer, fit with the paddle attachment, whip together granulated sugar, brown sugar, butter and applesauce on medium speed until pale and fluffy. Stir in eggs one at a time, mixing until combined after each addition. Stir in vanilla.
Working in 3 separate batches add 1/3 of the flour mixture alternating with half of the buttermilk beginning and ending with flour mixture and mixing just until combined after each addition.
Fold in zucchini. Pour mixture into a buttered 13 by 9-inch baking dish and bake in preheated oven 43 - 46 minutes, until toothpick inserted into center comes out clean or with a few moist crumbs. Allow to cool almost completely then frost with chocolate ganache.
FOR THE CHOCOLATE GANACHE: Heat cream in a small saucepan (or alternately you can microwave in a microwave safe dish) and bring just to a gentle boil.
Meanwhile place chocolate in a heat proof mixing bowl. Pour hot cream over chocolate and whisk mixture until smooth. Allow to cool 5 minutes before spreading over cake.