In a medium bowl, whisk together sugar, oil, eggs, and vanilla.
In a large bowl, whisk together flour, baking powder, salt, and cinnamon.
Add the wet ingredients to the dry ingredients, stirring until just combined.
Fold in grated zucchini and 1 1/2 cups chopped pecans.
Spread into the bottom of a lightly greased 13x9-inch baking pan.
Bake at 350 degrees for 35-40 minutes, or until top and edges are golden, and a toothpick inserted near the center comes out clean.
Remove to a wire rack to cool completely.
Meanwhile, prepare brown butter frosting.