Preheat the oven to 350℉/176℃ and grease a muffin tray.**(see notes if avoiding oil)
Squeeze out the excess moisture from your shredded zucchini over a bowl or your kitchen sink. Then place it in a bowl with the remaining wet ingredients and mix.
Whisk the dry ingredients in another bowl and add that to the wet bowl. Stir until no floury bits remain, without overmixing. Let the batter rest for 10 minutes, it will thicken slightly, and then give it a quick stir before dividing it between your 12 muffin cups.
Bake for 18-22 minutes, or until a toothpick inserted in the center comes out clean and dry. Let the muffins cool for at least 10 minutes in the pan, and then transfer them to a wire rack to continue cooling.
Notes
Use active baking powder for maximum lift. Baking powder that has been open in your pantry for 6+ months may start to lose its effectiveness.
You may use whole or ground flax seed for these muffins. Whole seeds add extra crunch and texture, and ground will offer maximum health benefits.
You may grate the zucchini using a box grater or food processor, either is fine.
For nut-free, just omit the walnuts or use chocolate chips or dried fruit for added sweetness.
Let the batter rest for 10 minutes before spooning it into your muffin pan for fluffier muffins. Give it a quick stir after 10 minutes and then divide and bake.
These muffins are NOT very sweet, so if you have a sweet tooth, I recommend using chocolate chips in place of the chopped nuts.
**If you have a good quality and relatively new, nonstick muffin pan, you won't need to grease it. I've tested both ways and my muffins did not stick to the pan. However, you MUST wait 10 minutes before attempting to transfer the muffins to your cooling rack.Muffins keep covered at room temperature for up to 3 days, refrigerated for up to 1 week, and frozen airtight for up to 3 months.