Preheat your oven to 350 degrees
Grease and line a loaf pan with parchment paper and set aside for now
Grate 2 large or 3 medium zucchini or calabacita squash and set them aside
In a large bowl, whisk 2 large eggs, 1/2 cup of brown sugar, 1/2 cup of granulated sugar, 1 teaspoon of pure vanilla extract, 1/3 cup of a neutral oil and 1/3 cup of sour cream until completely combined
Add 2 1/2 cups of the grated zucchini and mix to incorporate (no need to squeeze out the liquid, but discard any liquid left behind after grating)
Add 1 1/3 cups of all purpose flour, 1/2 cup of natural unsweetened cocoa powder, 1 teaspoon of baking soda, 1/2 teaspoon of baking powder, 1 teaspoon of espresso powder and 1/2 teaspoon of salt and mix until just combined
Fold in 1 cup of chocolate chips (I use semi-sweet, but any chocolate chips will work here!)
Transfer the batter into your prepared loaf pan
Bake in a 350 degree oven for 55-65 minutes or until a toothpick will come out of the center clean and it feels springy and set to the touch
Transfer the loaf pan onto a cooling rack and let cool for about 20 minutes before transferring the loaf out of the pan
Enjoy warm or at room temperature
Store leftovers in an airtight container at room temperature for up to 4 days