Preheat oven to 180 C (355 F) and line a loaf tin with baking paper.
Combine banana, greek yoghurt and grated zucchini in a mixing bowl.
Add self raising flour and mix until just combined.
Add walnuts and mix through.
Spread mixture evenly in prepared loaf tin.
Bake for 35 minutes, or until golden on top and a toothpick inserted into the middle comes out clean.
Allow to cool on bench, then store in the fridge for 3-5 days.
To freeze, wrap slices individually in plastic wrap and store in a freezer-safe bag or container.