Preheat oven to 350°F (175°C). Grease a muffin tin or line with paper liners.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
In another bowl, mix together the sugar, oil, eggs, and vanilla extract until well combined.
Stir the grated zucchini into the wet ingredients.
Gradually add the dry ingredients to the wet ingredients, stirring just until combined.
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 the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.