Preheat the oven to 350° F.
Line two loaf pans with parchment paper.
In a mixing bowl combine the flour, baking powder, baking soda, salt, and cinnamon.
Stir until everything is evenly distributed.
Crack the eggs into a separate large mixing bowl and beat them until they are pale yellow and smooth, about 2 minutes.
Add the sugar to the eggs and beat until well combined.
Add the oil, vanilla extract, and orange zest to the egg and flour mixture. Beat until well combined.
Grate the zucchinis and measure out one cup.
Add the grated zucchini to the wet mixture and stir thoroughly.
Add half of the flour mixture into the wet mixture and beat until combined.
When the first half of the dry mixture has been absorbed by the wet mixture, add the second half of the dry mixture and mix until well combined.
Add the blueberries and gently fold them into the batter until they are evenly distributed throughout. Use a rubber spatula to prevent the berries from splitting as much as possible.
Distribute the batter evenly between the two loaf pans.
Bake for approximately 50 to 60 minutes, but start checking the loaves after 45 minutes.
When done, the loaves will be medium brown; when you test them with a toothpick or sharp knife, the toothpick or knife will come out clean.
Let the loaves cool enough to slice, but serve while still warm enough to enjoy with butter.