Mackerel fillet from the oven

Cut the zucchini into large cubes and sprinkle with a little salt, let them rest for 10 minutes. Preheat the oven to 180 degrees. Heat 3 tablespoons of olive oil in a frying pan and gently fry the onion and garlic until translucent. Pat the zucchini dry with a little kitchen paper and spoon the cubes through the onion mixture. Fry the zucchini on high heat for 2 to 4 minutes until done and brown, toss in the raisins and oregano and add salt and pepper to taste. Rub the mackerel fillet with some lemon juice, salt and pepper. Divide the zucchini mixture in a greased oven dish and place the mackerel fillets on top. Mix the Greek yogurt with the egg, the rest of the lemon juice and the last spoonful of olive oil and pour this over the fish. Place the dish in the oven at 180 degrees and bake the mackerel fillets in about 20 minutes.