Preheat the oven to 425°F (220°C). Grease the muffin pan with non-stick oil spray or line it with paper liners, and set aside. If using paper liners, lightly grease them as well.
Whisk the flour, baking powder, baking soda, salt, and ground cinnamon in a medium bowl until well combined.
Add chocolate chips to the flour mixture and stir well. You can skip adding chocolate chips or add your choice of chopped nuts.
In a large bowl, whisk melted butter, oil, granulated sugar, brown sugar, sour cream, and vanilla until well combined. Add shredded zucchini and mix well.
Add dry ingredients to the wet mixture and gently mix until just combined. Do not overmix.
Divide the batter evenly between the muffin liners. Fill each muffin liner all the way up to the top. I recommend using an ice cream scoop for easy and even distribution of the batter.
Bake the muffins for 5 minutes at 425°F (220°C), and then, keeping the muffins in the oven, reduce the oven temperature to 350°F (180°C).
Continue baking for 15-17 minutes or until the cake tester inserted in the center comes out clean.
Because every oven is different, keep an eye on the oven after 15 minutes of baking.
Remove the muffins from the oven and let them cool in the pan for 5 minutes. Then transfer them onto a cooling rack and let them cool completely before serving.