Preheat the oven to 350°F (176°)
Prepare a 9x5 loaf pan with parchment paper, leaving some showing on the sides for easy removal. I also lightly grease with butter or cooking spray.
Add your butter to a small sauce pan or to a microwave-safe bowl and melt on low until completely melted. Set aside to let cool.
Grate zucchini and set aside.Whisk the flour, baking powder, baking soda, salt, cinnamon, nutmeg and cardamom together in a large bowl until combined. Set aside.
In a medium bowl, whisk the cooled butter, brown sugar, granulated sugar, eggs, room temperature cream cheese, and vanilla together until combined.
Pour the wet ingredients into the dry ingredients. Gently stir or whisk until combined.
Gently fold in zucchini first and any optional add-ins like chocolate chips.
Gently fold in blueberries to prevent crushing them.
Spread the thick batter evenly into your prepared loaf pan.
Bake for 55-70 minutes. Baking times vary, so keep an eye on yours, checking for doneness every 5 minutes at the 55-minute mark. The bread is done when a toothpick inserted in the center comes out clean.
Remove the bread from the oven and allow it to cool before removing from the pan.