Preheat oven to 350°F (175°C). Grease or line a 9x5-inch loaf pan with parchment paper.
Shred zucchini using a box grater, then wrap in a clean kitchen towel and squeeze out excess liquid. Set aside.
In a large mixing bowl, whisk eggs, oil, brown sugar, granulated sugar, and vanilla until smooth.
Add flour, baking soda, baking powder, salt, and cinnamon (if using). Stir gently until just combined.
Fold in shredded zucchini, then chocolate chips.
Pour batter into the loaf pan, smoothing the top. Sprinkle with extra chocolate chips if desired.
Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool in pan for 10 minutes, then transfer to a wire rack. Let cool completely before slicing.