Preheat oven to 350 degrees. Butter and flour 2 loaf pans and set aside. I actually used one 8" disposable pan to give away and a larger 9" one for me and the batter divided perfectly. So you should get 2 very full 8" pans or slightly less full 9".
Mix topping ingredients in a small bowl and set aside.
2 Tablespoons brown sugar, 2 Tablespoons white sugar, 1/2 teaspoon cinnamon
Place flour, cinnamon, baking soda, salt, and cocoa powder in a small bowl and whisk to combine. Set aside.
With a stand or hand mixer beat oil, white sugar, brown sugar, and eggs until combined and slightly fluffy, 1-2 minutes.
1/2 cup canola oil, 7.5 ounces granulated sugar, 1.9 ounces brown sugar, 3 large eggs
Add vanilla and sour cream and mix until combined.
2 teaspoons vanilla extract, 1/2 cup sour cream
Gently stir in the grated zucchini (and zest if you’re using).
3 cups grated zucchini, zest from one orange
Take a spoonful of the flour mixture and stir in with the chocolate chips (that will help keep them evenly distributed.) If you only have regular chocolate chips, or a chocolate bar, just give it a chop so it’s the size of mini chocolate chips.
3/4 cup mini chocolate chips
Add the remaining flour mixture to the batter and stir just until combined. Add chocolate chips and stir to combine.
Divide the batter between the two pans. Sprinkle the chocolate chips and the sugar topping over each. Place pans on a cookie sheet for easy moving.
2 Tablespoons mini chocolate chips
Bake in your preheated 350 degree oven for 50-60 minutes.
When it’s done a toothpick or skewer should come out without goopy batter on it and the top will be gorgeous and cracked with sugar.
Let it cool on a rack for 5-10 minutes and then remove from pans.
You will need about 2 large zucchinis or 3 medium zucchinis to yield 3 cups grated. You don't want your grated zucchini overly wet, nor do you want it dry. Give it a gentle pat with a paper towel or tea towel before incorporating if it needs it.
There's no need to peel zucchini before grating it, especially for zucchini bread. You won't be able to tell the skin has been left on as it softens when baked. Wash your zucchini before grating and you're good to go!