Heat oven to 350 degrees and prep 3, 8-inch cake pans butter and flour or baking spray. Cut a parchment round for the bottom of each pan and place inside. I always use cake strips, which prevent my cake layers from doming.
Mix together flour, cocoa powder, baking soda, baking powder, espresso powder (optional), and salt in a large bowl. Sifting will break up any lumps of cocoa powder but is not a must.
Mix oil, granulated sugar, brown sugar, eggs, sour cream, and vanilla together in a second large bowl. If using a stand mixer use a paddle attachment.
Add the shredded zucchini to the wet mixture and mix on low to combine.
Add the dry to the wet and mix on low until almost combined then add in chocolate chips and mix until distributed. Scrape the bowl down and use a spatula to mix in any stray bits of flour etc.
Distribute cake batter evenly to your three prepared pans and bake for 30-35 minutes, or until centers are springy to the touch and a skewer inserted in the middle comes out clean.
Allow cakes to cool in pans for a couple minutes then invert onto a wire rack, and remove parchment paper rounds. Allow to cool completely