Step 1Heat the oven to 350 degrees. Grease a 10-inch springform cake pan and sprinkle with cocoa powder to coat. Tap out any excess.
Step 2In a large bowl, stir together the flour, cocoa powder, baking soda, baking powder and salt.
Step 3In a food processor, combine the butter and brown sugar. Pulse until fluffy. Add the vanilla extract and instant coffee and pulse to combine. Add the eggs, one at a time, and pulse to mix between each addition. Scrape the bowl after each addition.
Step 4Reserve one-half cup of the flour mixture and set aside. Spoon the rest of the flour mixture into the food processor and pulse until smooth. The batter will be thick.
Step 5Combine the grated zucchini, chocolate chips and reserved flour mixture and toss to coat. Fold the zucchini mixture into the cake batter, blending thoroughly.
Step 6Scrape the batter into the prepared pan and smooth the surface with a spatula.
Step 7Sprinkle chopped hazelnuts over the batter. Bake until a cake tester comes out clean, about 40 to 50 minutes.
Step 8Cool on a rack for about 30 minutes, then unmold and serve.