Prepare the Zucchini: Wash and finely shred the zucchini. If it is very watery, gently squeeze out some excess moisture, but do not dry it completely. Set aside.
Make the Cheesecake Filling: Add the softened cream cheese to a mixing bowl and beat until smooth. Add the powdered sugar, egg yolk, and vanilla extract. Beat until creamy and lump-free. Set aside.
Combine the Dry Ingredients: In a separate bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt until evenly combined.
Prepare the Wet Mixture: In a large bowl, whisk together the eggs, granulated sugar, brown sugar, vanilla extract, and vegetable oil until smooth.
Make the Chocolate Batter: Gradually add the dry ingredients to the wet mixture. Stir gently until just combined. Fold in the shredded zucchini and optional mini chocolate chips. Do not overmix.
Prepare the Loaf Pan: Preheat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with parchment paper, leaving some overhang for easy removal.
Add the First Layer: Spread about half of the chocolate zucchini batter evenly into the prepared loaf pan.
Add the Cheesecake Layer: Spoon the cheesecake mixture over the chocolate batter and gently spread it into an even layer, leaving a small border around the edges.
Add the Remaining Batter: Carefully spread the remaining chocolate zucchini batter over the cheesecake layer, covering it as evenly as possible.
Create the Swirl: Use a butter knife to gently make several swirling motions through the batter. Do not over-swirl, as you want distinct ribbons of cheesecake throughout the chocolate bread.
Bake the Bread: Place the loaf in the preheated oven and bake for 50–55 minutes, or until the chocolate portion is set and a toothpick inserted into the bread comes out with a few moist crumbs.
Cool the Loaf: Let the bread cool in the pan for about 15 minutes. Carefully lift it out using the parchment paper and transfer it to a wire rack. Allow it to cool completely before slicing.
Slice and Serve: Once completely cooled, use a sharp knife to cut the loaf into slices. Serve with coffee, tea, fresh berries, or a scoop of vanilla ice cream.