Preheat your oven to 350°F (175°C). Grease and flour the loaf pan or line it with parchment paper.
In a large mixing bowl, combine the all-purpose flour, baking powder, baking soda, salt, and ground cinnamon. Whisk together until well blended.
In a medium mixing bowl, whisk the granulated sugar, brown sugar, eggs, vegetable oil, and vanilla extract until smooth.
Stir in the mashed bananas and grated zucchini into the wet mixture until fully combined.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Be careful not to over-mix.
Gently fold in the blueberries into the batter.
Pour the batter into the prepared loaf pan and spread it evenly.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and allow to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.