Preheat oven to 350°F. Grease 12 muffins cups or line with non-stick cupcake wrappers.
Place the shredded zucchini in a mesh sieve or colander and press with the back of a spatula until most of the water is released.
Whisk gluten free flour and baking powder together in a large bowl. In a medium sized bowl, combine olive oil, sugar, eggs, almond milk, salt, zucchini, and lemon zest. Whisk to combine.
Pour the wet ingredients into the dry ingredients and mix gently to combine. Distribute evenly into the muffin cups, filling each to approximately ¾ full. Bake for 20–25 minutes, or until a toothpick inserted into a muffin returns small crumbs.
Let muffins cool for 10 minutes and then remove to a cooling rack to cool completely.
In a small bowl, whisk together the powdered sugar and lemon juice until it reaches a consistency for drizzling. Add more lemon juice or powdered sugar if necessary.
Drizzle about 1 teaspoon glaze over each muffin, and serve.