Preheat oven to 350°F and line or lightly grease a 12-cup muffin pan.
Grate the zucchini and carrots. Squeeze the zucchini well to remove excess moisture.
Add banana, spinach, Greek yogurt, maple syrup, avocado oil, eggs, and vanilla to a blender. Blend until smooth.
In a large bowl, whisk together flour, cacao powder, baking powder, baking soda, and salt.
Pour the blended wet ingredients into the dry ingredients and stir until just combined.
Fold in the squeezed zucchini, carrots, and chocolate chips. Do not overmix.
Divide batter evenly between muffin cups and add extra chocolate chips on top, if desired.
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out mostly clean.
Cool in the pan for 5 minutes, then transfer to a wire rack to finish cooling.