Put the fish into a bowl. Whisk together the lemon juice, oil, oregano, garlic and salt and pepper to season in a small bowl, or shake together in a screw-top jar. Drizzle 1 1/2 tablespoons of the mixture over the fish and turn it with your hands to coat in the marinade. Set aside.
Put the bacon onto a board and gently stretch it with the back of a knife. Cut each rasher into four pieces. Wrap a piece of bacon around each piece of fish, then thread onto eight oiled skewers, alternating with slices of zucchini.
Preheat the grill to a moderate heat. Use a pastry brush to coat the kebabs all over with the reserved marinade mixture, then place them on the grill rack.
Grill for 12–15 minutes, turning from time to time, until the zucchini is tender and the bacon is browned and crispy. To keep the zucchini moist, baste it while cooking with leftover marinade. Check that the fish is cooked by sliding a piece off a skewer and cutting it open; it should be opaque and flake easily. Serve hot, with lemon, pita bread and salad.