Preheat oven to 350°F and grease and line your loaf pan with parchment paper.
In a medium sized bowl, grate zucchini until you have 2 packed cups worth. Transfer the zucchini to a cheese cloth and squeeze the moisture out of it until almost no juice comes out when you squeeze. Set the squeezed and de-juiced zucchini aside.
In a saucepan or in the microwave, melt your butter. Set aside to cool.
In a large bowl add your flour, cocoa powder, baking powder, baking soda, and salt. Whisk to combine.
In a clean medium-sized bowl, add the sugars and the melted butter, whisk to combine completely.
Add the eggs, vanilla, and buttermilk and whisk together until you have a homogeneous liquid mass.
Pour the wet ingredients into the dry ingredients and whisk until everything is just combined and there are only a couple streaks of flour left.
Add your zucchini and fold it into the batter using the rubber spatula. Make sure it gets evenly distributed.
Pour your batter into your prepared loaf pan and top with chocolate chips if desired.
Bake in the preheated oven for 40-50 minutes or until a toothpick inserted in the center comes out clean.
Allow to cool before cutting and enjoy!