Preheat the oven to 175 degrees Celsius.
Shred the zucchini and squeeze out the water.
Combine the ingredients for the crumble and set aside.
Add egg and sugar to a blender and mix until smooth and a little fluffy.
Next add the mashed banana and yogurt and mix again.
Combine all the dry ingredients in a bowl.
Add dry ingredients to the wet and combine until you have a smooth batter.
Fold in the shredded zucchini using a spoon.
Fill 3/4 of muffin cups/forms and sprinkle with crumble on top.
Bake in the oven for 18-22 minutes until a toothpick comes out clean.
Let them cool before eating.