For the streusel topping:
Into a medium size mixing bowl add brown sugar, butter, oats, and flour. Stir to combine then set aside.
For the muffins:
Preheat oven to 350 degrees F and line 12 muffin cups with paper liners or grease with cooking spray.
Prepare a flax seed "egg" binder by whisking flax seed and water together in a small bowl. Allow to stand 5 minutes; mixture will thicken slightly.
To a large mixing bowl, add flour, brown sugar, white sugar, baking soda, cinnamon, and salt. Stir to combine.
To a medium size mixing bowl, add olive oil, almond milk, flax mixture, and vanilla bean paste. Whisk until well combined. Stir into flour mixture.
Fold blueberries and zucchini into batter.
Divide batter evenly into 12 muffin cups. Sprinkle with an even layer of streusel topping over each muffin.
Bake 25 minutes or until a toothpick inserted in the center of a muffin comes out clean. Serve warm or room temperature.