1. Preheat oven to 350°F (175°C). Grease or line a 9×13-inch baking pan with parchment paper.

2. Finely shred zucchini using a box grater or food processor. Pat with a paper towel to remove excess moisture.

3. In a large bowl, whisk together flour, cocoa powder, baking soda, and salt.

4. In a separate bowl, beat eggs, granulated sugar, and brown sugar until light. Add oil and vanilla extract, mixing until smooth.

5. Stir shredded zucchini into the wet mixture. It will seem thick at first but loosens as the zucchini releases moisture.

6. Fold dry ingredients into wet using a rubber spatula. Do not overmix. Stir in chocolate chips or chunks if using.

7. Pour batter into prepared pan and spread evenly. Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

8. Cool in pan for 15 minutes. Transfer to a wire rack and let cool completely before slicing into squares.