Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Line muffin pans with paper liners and set aside.

Combine the zest of the three fruits in a small bowl. Remove about a third of it to use in glaze. Add sugar to bowl and stir to distribute.

In a medium bowl, whisk together sugar and zest mixture, oil, eggs, baking soda, baking powder, vanilla, and salt.

Measure out 1/2 cup of the citrus juice and add to the bowl. (Save the rest for a different use.) Add milk and whisk to combine.

Using a sturdy spoon, stir in flour until completely smooth. Pour batter into prepared muffin pans, filling each cup about three-quarters full. Bake for 16–18 minutes, until tops are set. Set aside to cool completely before glazing.

In a small bowl, whisk to combine all ingredients.

Add a few drops of water, as needed, to reach desired consistency. Drizzle over cooled muffins.