Coat the inside of the Bundt cake pans with a light non-stick spray. Give a light dusting of cocoa powder over the non-stick spray. Set aside.
Use a cheese grater to grate enough zucchini for the recipe. No need to squeeze out the extra liquid for this recipe. Measure out the zucchini and set aside.
Preheat the oven to 350F. Make sure the oven rack in the middle position, and that there is enough clearance over it to fit the Bundt cake pans.
Combine in a bowl, the flour, cocoa powder, baking soda, and salt. Whisk until ingredients are well blended.
In a larger, separate bowl, add the cracked eggs, oil, vanilla, brown sugar, and granulated sugar. Whisk until smooth. Add the yogurt and whisk to combine. Use a rubber spatula to fold the grated zucchini into the wet ingredients.
Add the dry ingredients to the wet ingredients. Stir with a spatula, just until the dry ingredients have been completely absorbed. Add the the optional chocolate chips and/or shredded coconut and stir in.
Divide the batter equally into the 2 prepared Bundt cake pans. Use a cooking scale to do this if you have one.
Place the Chocolate Zucchini Bundt Cakes into the preheated 350F oven. Bake for 40-45 minutes or until a toothpick inserted in the middle comes out clean. Let the cakes cook for 5-10 minutes before unmolding them. Hold the cake mold, right side up, lightly tapping it on its side to help release the cake before flipping it onto a plate. Let the cakes cool completely before glazing.