Preheat and Prep: Preheat your oven to $375^{circ}$F ($190^{circ}$C). Line a 12-cup muffin tin with paper or silicone liners.
Combine Dry Ingredients: In a large mixing bowl, whisk together the whole wheat pastry flour, protein powder, almond flour, baking powder, baking soda, cardamom, cinnamon, and salt. Whisking thoroughly ensures the leavening agents are evenly distributed, which helps the muffins rise properly.
Combine Wet Ingredients: In a separate medium bowl, add the Greek yogurt, olive oil, maple syrup, eggs, vanilla extract, orange zest, and orange juice. Whisk until the mixture is smooth and emulsified. The orange zest is key, so don't skip it!
Grate and Squeeze Zucchini: If you haven't already, grate your zucchini. Place the shreds in the center of a clean kitchen towel or several paper towels. Gather the ends and twist firmly to squeeze out as much liquid as possible. You should be left with a compact ball of zucchini pulp.
Combine Wet and Dry: Pour the wet ingredients into the large bowl with the dry ingredients. Using a spatula, gently fold the mixtures together until they are just combined. There may still be a few small flour streaks. Do not overmix, as this will develop gluten and result in tough, dense muffins.
Fold in the Good Stuff: Add the squeezed zucchini and half ⅓ of the chopped pistachios to the batter. Gently fold another 2-3 times until they are just incorporated.
Fill Muffin Cups: Divide the batter evenly among the 12 prepared muffin cups. They will be quite full, about ¾ to the top.
Add Topping: Sprinkle the remaining ⅓ cup of chopped pistachios evenly over the tops of the muffin batter.
Bake: Place the muffin tin in the center of the preheated oven. Bake for 18−22 minutes. The muffins are done when they are golden brown on top and a wooden toothpick inserted into the center of a muffin comes out clean or with a few moist crumbs attached.
Cool: Let the muffins cool in the tin for 5-10 minutes before transferring them to a wire rack to cool completely. Allowing them to cool completely is important for the texture to set.
(Optional) Prepare and Apply Glaze: Once the muffins are completely cool, whisk together the powdered sweetener/sugar and 1 tsp of orange juice. If it's too thick, add more juice, a tiny drop at a time, until you have a drizzling consistency. Lightly drizzle the glaze over the tops of the muffins.