Preheat the oven to 350 and prepare a 9x5-inch loaf pan with grease and parchment paper. Set to the side.
Combine the cinnamon and sugar for the topping in a small bowl. Set to the side.
Mix the flour, baking soda, cream of tartar, salt, and cinnamon in a medium-sized bowl. Set to the side.
Using a whisk, mix the oil, eggs, granulated sugar, brown sugar, whole milk, and vanilla. Mix until combined, then fold in the shredded zucchini.
Pour half the batter into the prepared loaf pan. Then, add half of the cinnamon sugar topping to the batter. Pour in the rest of the batter, followed by the rest of the cinnamon sugar topping.
Bake the loaf in the oven for 55-65 minutes. The top layer of cinnamon sugar will form a crust on top of the loaf. When done, let it cool to room temperature before slicing.