Preheat oven to 350 degrees. Grease and flour an 8-inch bread pan.
In a large bowl, combine zucchini, sugar, oil, vanilla, and eggs, and mix well.
Add 1/2 cup of flour to the mixture, along with the baking soda, cinnamon, salt, and baking powder. Mix well.
Add the remaining 1 cup of flour and stir until incorporated.
In a small bowl, mix together the 1/4 cup of sugar and 1 Tbsp. cinnamon.
Pour 1/3 of the batter into the prepared bread pan. Sprinkle half of the cinnamon sugar mixture over the top. Add another 1/3 of the batter, then sprinkle with the remaining cinnamon sugar mixture. Pour the last 1/3 of the batter over the top.
Bake for 35-45 minutes, until an inserted toothpick comes out clean.