Preheat the oven to 180℃ (top/bottom heat mode) or 170℃ (fan-assisted).

Grease the baking pan with butter and dust with flour or breadcrumbs (you can also line it with baking paper).

In a large bowl, mix together the dry ingredients for the cake.

In a second bowl, thoroughly mash the bananas with a fork.

Add eggs and oil to them and mix.

Pour the wet ingredients into the dry ones.

Mix into a batter - it will be quite thick.

Grate the zucchini on a coarse grater - if it's very juicy, you can lightly squeeze out the excess liquid.

Add the zucchini to the batter and mix thoroughly with a spatula.

Transfer the batter to the prepared pan.

Place the pan in the oven and bake for about 45 minutes - until a dry skewer comes out.

After baking, cool the cake completely before pouring the glaze over it.

Sift the powdered sugar into a bowl and gradually add milk - mix until you get a thick and slightly runny glaze.

Coat the top of the cake with it.