Preheat your oven to 350°F (175°C) and grease a 9x9 inch baking pan.

In a large bowl, combine the grated zucchini, vegetable oil, granulated sugar, brown sugar, eggs, and vanilla extract. Mix until well combined.

In another bowl, whisk together the flour, cocoa powder, baking soda, salt, and ground cinnamon (if using).

Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.

Fold in the chocolate chips, if using.

Pour the brownie batter into the prepared baking pan and spread it evenly.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out mostly clean.

Allow the brownies to cool in the pan before cutting them into squares and serving.