Preheat the oven to 350°F (175°C) and grease a muffin tin or line with muffin liners.

In a mixing bowl, whisk together the dry ingredients: flour, baking powder, baking soda, salt, cinnamon, and nutmeg.

In another bowl, combine the wet ingredients: Greek yogurt, honey, eggs, and vanilla extract. Mix until smooth.

Add the grated zucchini to the wet mixture and stir to combine.

Gradually fold the dry ingredients into the wet ingredients until just combined. Avoid overmixing.

If desired, fold in walnuts or chocolate chips.

Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.

Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.