Wash the zucchini, trim the ends, then cut into batons or slices. Coat in olive oil and grill on a grill pan or fry in a regular pan. At the end season with salt and pepper. At the very end mix with grated garlic and dried oregano.
Arrange the lettuce on a platter, add chopped tomato (can be blanched and peeled beforehand). Sprinkle with thinly sliced onion. Add the zucchini and sprinkle with diced feta. Season with pepper and salt if needed.
Mix the vinaigrette ingredients (e.g. in a closed jar, shaking it vigorously) and drizzle over the salad.