Add the oregano, red pepper flakes, salt, olive oil and lemon zest. Separate into two bowls and toss well to coat the chicken in one bowl and the vegetables in the other bowl of seasonings. Working one skewer at a time, thread one piece of chicken, followed by a piece of zucchini, then a tomato, piece of pancetta, then chicken, zucchini, tomato, pancetta and lastly chicken. Continue with the remaining chicken, veggies and pork.