Preheat oven to 180°C (350°F) and line a 12-cup muffin tray with paper liners.
In a blender or food processor, add eggs, banana, carrot, zucchini, apple, spinach, melted butter (or oil), honey (or maple syrup), and ACV. Blend until smooth.
Add the flour, baking powder, baking soda, cocoa powder, salt, and (optional) collagen powder or extra flour if not using. Blend again just until combined—avoid overmixing.
Remove the blender blade or transfer the batter to a bowl. Gently fold in the chocolate chips.
Divide the batter evenly among the muffin cups.
Bake for 20–25 minutes, or until a toothpick inserted into the center comes out clean.
Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
