Preheat oven to 350°F and prepare a 9x13 inch pan with butter or baking spray and line with parchment paper, allowing it to go up the sides for easy removal.

In a large bowl, combine vegetable oil, sugar, and vanilla extract until fully incorporated.

Add flour, cocoa powder, baking soda, and salt. Mix until just combined; batter will be thick.

Fold in shredded zucchini by hand. Let batter rest for 5 minutes to hydrate the zucchini.

Stir in chocolate chunks until evenly distributed. Rest for an additional 5 minutes if batter appears dry.

Spread the batter into the prepared pan and bake for 25-35 minutes, until a toothpick inserted comes out with crumbs, not wet batter.