Wash zucchinis thoroughly under cold water and grate using a box grater or food processor. Squeeze out excess moisture with a clean kitchen towel or cheesecloth to prevent soggy muffins.

In a large bowl, whisk together flour, baking powder, baking soda, garlic powder, onion powder, black pepper, and salt until fully blended.

In a separate bowl, whisk eggs until frothy. Add milk, olive oil, and parsley if using, mixing gently until combined.

Pour the wet mixture into the dry ingredients and fold gently with a spatula until combined, being careful not to overmix.

Fold in grated zucchini, Parmesan, and mozzarella until just incorporated. The batter should be thick and moist.

Preheat oven to 375°F (190°C) and grease a muffin tin or line with paper liners.

Spoon batter into muffin cups, filling about ¾ full, and sprinkle breadcrumbs evenly on top for a light crunch.

Bake for 20–25 minutes, or until golden brown and a toothpick inserted in the center comes out clean.

Allow muffins to cool in the tin for 5 minutes before transferring to a wire rack. Serve warm or at room temperature, optionally with sour cream or yogurt.