Wash the herbs, dab dry and chop finely, except for a little to garnish. Put 1 tablespoon of parsley aside. Peel the garlic and press it through a garlic press. Wash the lemon thoroughly, dab dry and peel the lemon peel in fine strips with a julienne chaff.
Squeeze the lemon and mix the juice with the remaining herbs, garlic and lemon julienne. Wash the cod fillet, dab dry and cut into 4 equal pieces. Spread the herb marinade over the fish and leave covered.
Wash and peel the potatoes and cook them in boiling salted water for about 20 minutes. Peel and finely chop the onion. Clean oyster mushrooms and cut in half or quarters. Clean and wash the zucchinis and cut them lengthwise into thin slices with a wide peeler.
Heat 30-40 g fat in a frying pan and fry the mushrooms vigorously while turning. Add the onion, fry briefly and finally fry the zucchini slices. Season zucchini-mushroom vegetables with salt and coloured, coarsely ground pepper.
Remove the fish fillets from the marinade and salt them. Heat the remaining fat in another pan and fry the fillets for 4-5 minutes while turning. Arrange fish fillets, vegetables and potatoes on plates.
Serve garnished and sprinkled with lemon slices and remaining parsley.