Preheat the oven to 350F degrees and line a 9-inch square baking pan with parchment paper and set aside.
Add 1 1/2 cups diced zucchini, 1/4 cup vegetable oil, 3 large eggs and 1 teaspoon vanilla extract to a food processor or blender and blend until smooth.
Pour the mixture into a large mixing bowl or stand mixer bowl. In a separate bowl, whisk together 1/2 cup all-purpose flour, 2/3 cup granulated sugar, 2/3 cup unsweetened cocoa powder, 1/2 teaspoon baking powder and 1/2 teaspoon salt - add the dry ingredients to the wet ingredients and mix just until combined.
Fold in 1/2 cup mini chocolate chips and pour the batter into the prepared baking pan.
Bake for 25 to 30 minutes. Remove from the oven and allow to cool for about an hour then top with chocolate frosting (if using.) Slice and serve.
Video
Notes
You can make a homemade chocolate frosting or use store-bought.