Mix zucchini and salt in medium bowl. Transfer to a colander; set over bowl. Let stand 15 minutes to drain liquid from zucchini. Rinse and drain zucchini. Squeeze zucchini to remove liquid.
Heat oil in large skillet over medium heat. Add zucchini and sauté 2 minutes. Remove pan to a bowl, cool slightly. Add ricotta, Parmesan and lemon peel to zucchini. Stir to blend. Season to taste with salt and pepper.
Preheat broiler. Arrange bread pieces cut side up on baking sheet. Broil bread just until lightly toasted. Spread ricotta mixture generously over 8 focaccia pieces. Broil until ricotta mixture is heated through and beginning to brown in spots, about 4 minutes.
Top 4 bread pieces with tomato slices, then with chicken slices, dividing equally. Sprinkle with salt and pepper. Cover with remaining 4 bread pieces, ricotta-mixture side down. Cut sandwiches diagonally in half and serve.
