Preheat your oven to 350 degrees Fahrenheit and prepare a 9-inch by 13-inch rectangular pan (or equivalent size) by greasing it and lining the bottom and sides with parchment paper.
In a large bowl, combine the melted butter, oil, sugar, eggs, vanilla, buttermilk, and shredded zucchini with a whisk until well combined.
To a separate bowl (or in the same bowl, on top of the wet ingredients), add the flour, cocoa, baking soda, cinnamon, cloves, and salt.
Mix together well with a spatula until combined and no streaks of flour remain.
Pour the batter into the prepared pan immediately and sprinkle the chocolate chips over the top of the batter.
Bake at 350 degrees Fahrenheit for 25 to 30 minutes or until a toothpick inserted into the middle of the cake comes out clean.
Allow the cake to cool in the pan until cooled completely before slicing and serving.
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Notes
This cake keeps well in an airtight container at room temperature for about 3 days, and in the freezer for about 3 months.