Preheat Oven and Prep Pan:
Heat oven to 425°F (220°C). Coat muffin pan with spray or line with paper liners.Mix Dry Ingredients:
In a large bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg until uniform. If using optional chocolate chips or nuts, fold them into the dry mix. Set aside.Combine Wet Ingredients:
In a separate medium bowl, combine oil, applesauce, brown sugar, granulated sugar, egg, vanilla, and shredded zucchini; stir until well blended.Fold Batter Together:
Pour dry ingredients into wet mixture and fold gently until no dry streaks remain. Avoid overmixing.Fill Muffin Cups:
Divide batter evenly among muffin cups, filling each to the brim.Bake with Temperature Change:
Bake at 425°F (220°C) for 5 minutes. Without removing muffins, lower oven temperature to 350°F (175°C) and continue baking for 13–15 minutes, until a toothpick inserted in center emerges mostly clean. The initial high heat creates a rise, then the lower temperature bakes the interior.Cool and Release Muffins:
Take muffins out of oven and let them rest in the pan for 10 minutes, then transfer to a wire rack to cool fully. If needed, run a knife around the edges to release.