Preheat oven to 350. Spray an 8-inch bread pan with nonstick cooking spray. In a large bowl combine zucchini, sugar, oil, vanilla, and eggs and mix well.
Add flour, baking soda, cinnamon, salt, and baking powder to a smaller bowl and whisk to combine. Add dry ingredients to wet ingredients and mix until all ingredients are incorporated.
In a small bowl whisk together cinnamon and sugar for the swirl.
Pour 1/3 of the batter into prepared pan. Sprinkle with 1/2 of the cinnamon-sugar mixture. Add another 1/3 of the batter, then the remaining cinnamon-sugar. Top with remaining 1/3 of the batter.
Bake 45 minutes then cover with aluminum foil and bake another 10-15 minutes or until an inserted toothpick comes out clean.