Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.

In a large bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg.

In a separate bowl, beat together the granulated sugar and vegetable oil until well combined.

Beat in the eggs one at a time, then stir in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the grated zucchini until evenly distributed.

Pour the batter into the prepared baking pan and spread evenly.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Let the bars cool completely in the pan on a wire rack.

In a medium bowl, beat the softened cream cheese and butter together until smooth and creamy.

Gradually add the powdered sugar, mixing until well combined and smooth.

Stir in the vanilla extract.

Once the zucchini bars have cooled completely, spread the cream cheese frosting evenly over the top.

Cut into bars and serve.