Preheat your oven to 350°F and grease a standard 12-cup muffin pan with coconut oil or cooking spray. While the oven heats, grate your zucchini and squeeze it firmly in a clean kitchen towel or cheesecloth to remove excess moisture—this is crucial for muffins that aren't dense or soggy. Let the grated zucchini sit in the towel while you prepare the other ingredients.
In a large mixing bowl, whisk together the wheat flour, cinnamon, baking powder, baking soda, ginger, nutmeg, and sea salt. Whisk for about 30 seconds to fully combine and aerate the mixture—this ensures the leavening agents are evenly distributed throughout the batter for consistent rise. Set this dry mixture aside.
In a separate bowl, whisk together the room-temperature egg, maple syrup, milk, cooled melted coconut oil, and vanilla extract until well combined and slightly frothy. Having the egg at room temperature helps it incorporate more smoothly into the batter. This wet mixture should be homogeneous before combining with the dry ingredients.
Pour the wet mixture from Step 3 into the dry ingredient mixture from Step 2 and gently fold together with a spatula until just combined—don't overmix, as this can lead to tough muffins. A few lumps are perfectly fine. Now add the squeezed zucchini from Step 1 and the old-fashioned oats, folding gently until evenly distributed throughout the batter. I like to do a final gentle stir to make sure the zucchini isn't clumpy in any one area.
Divide the batter evenly among the 12 greased muffin cups, filling each about three-quarters full. Sprinkle the chopped walnuts and turbinado sugar over the top of each muffin. The turbinado sugar adds a nice textural contrast and slight crunch to the top, plus it catches the heat beautifully as they bake.
Place the muffin pan in your preheated 350°F oven and bake for 16–18 minutes, until a toothpick inserted into the center of a muffin comes out clean or with just a few moist crumbs. The muffins should be golden brown on top. Remove from the oven and let cool in the pan for 5 minutes before carefully removing them to a wire rack to cool completely.