Preheat oven to 350°F. Spray a 9x13-inch baking dish with non-stick cooking spray.

In a medium bowl, combine granulated sugar, brown sugar, cinnamon, and nutmeg. Stir well.

Add vegetable oil and vanilla extract, mixing until incorporated.

Add eggs one at a time, whisking until fully combined after each addition.

In a separate bowl, whisk together flour, baking soda, baking powder, and salt.

Gradually add dry ingredients into wet ingredients, mixing until just combined.

Gently fold in grated zucchini with a spatula.

Pour batter into prepared baking dish and smooth the top.

Bake for 60 minutes or until a toothpick inserted in the center comes out clean.

Remove from oven and allow to cool completely before frosting.

For frosting, beat cream cheese and butter until smooth and creamy.

Gradually add confectioners' sugar, vanilla, and milk, beating until fluffy.

Spread frosting evenly over cooled cake. Slice and serve.