1. Blend or finely chop the fish fillets.
2. Cut the zucchini into small pieces and steam or boil them (if boiling, make sure to drain well after cooking).
3. Blend the shallot and parsley, and sauté them in a pan with a little olive oil.
4. Meanwhile, cook the fish fillets (e.g. 4 minutes in boiling water in the microwave, covered).
5. Mash or pass the zucchini through a food mill, and mix with the shallots, fish, and Greek yogurt (about 1 large tablespoon).
6. Season with salt, pepper, and spices; mix well.
7. Place everything in an ovenproof dish, sprinkle with breadcrumbs, and bake in a preheated oven or under the broiler.
8. Wait until the breadcrumbs are slightly toasted on top, remove from the oven, and serve.