Preheat oven to 425 degrees Fahrenheit.

In a large bowl, combine flour, cornmeal, baking powder, and salt.

Add milk and vegetable oil to the dry ingredients.

Stir until the mixture forms a ball.

Turn the dough out onto a greased 14-inch round pizza pan.

Let the dough rest for 2-3 minutes.

Using the back of a large spoon or your hands, press the dough to fill the pan.

Shape the edge of the dough to form a rim.

Bake the crust for about 15 minutes.

Remove the partially baked crust from the oven.

Spread pizza sauce evenly over the crust.

Arrange the green bell pepper rings, onion rings, and zucchini slices on top of the sauce.

Sprinkle mozzarella cheese and parmesan cheese over the vegetables.

Bake for another 15-20 minutes, or until the crust is golden brown and the cheese is melted and bubbly.