Preheat the oven to 350°F. Prepare a 9x5x3 inch loaf pan by spraying with cooking spray or coating in butter. Set aside.
In a medium saucepan, melt butter over medium-high heat. Once melted completely, reduce the heat slightly and allow to simmer until it becomes a golden-brown color and smells nutty and fragrant. Set aside and allow to cool slightly.
Meanwhile, in a large bowl, combine the all-purpose flour, whole wheat flour, sugar, baking powder, baking soda, salt and cornmeal until uniformly mixed.
To the cooled butter, add the buttermilk and eggs and whisk together until well combined. {I just did this right in the saucepan as not to have to dirty another bowl.} Mix in the shredded zucchini.
Add the wet ingredients to the dry ingredients and fold together until there are no more dry spots, but try not to overmix. The batter is going to be very thick; it should be.
Scoop the batter into the prepared loaf pan and spread it as evenly as possible. Bake for about 55 minutes to 1 hour or until a skewer inserted in the center comes out mostly clean. {It's a moist bread so it may have some sticky crumbs, just make sure that it's not uncooked batter and you should be fine.}
Remove from oven and cool in the pan for about 15 minutes before removing and slicing.