Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with olive oil.
In a large bowl, combine the flour, baking powder, salt, and black pepper. Mix well.
In another bowl, whisk together the eggs and milk until well combined.
Gradually add the egg mixture to the flour mixture, stirring until smooth.
Fold in the sliced zucchini, onion, Parmesan cheese, basil, and parsley until evenly coated.
Pour the mixture into the prepared baking dish and spread it out evenly.
Drizzle the olive oil over the top of the mixture.
Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Let it cool for 5-10 minutes before slicing and serving.