Preheat the oven to 375 degrees F. Line a muffin tin with liners.
In a small bowl, whisk together the flour, sugar, baking soda, cinnamon and salt.
In a larger bowl, whisk together the egg, oil, milk, lemon juice and vanilla extract. Stir the dry ingredients into the wet ingredients until just combined. Stir in the zucchini and blueberries until just mixed.
Fill the muffin liners ¾ of the way full. Bake for 20 to 22 minutes, or until a tester inserted in the center comes out clean.
Let the muffins cool, then drizzle them with the lemon glaze.
Whisk together the ingredients until smooth and drizzle-able. If it’s too thick, add a bit more lemon juice 1 teaspoon at a time. If it becomes too thin, whisk in a bit more powdered sugar ¼ cup at a time. Drizzle over the muffins!