Heat the oil in medium non-stick skillet over medium heat. Add the onion and cook until soft, about 4 minutes. Add the zucchini, the salsa, and a couple tablespoons of water. Cover, cook for 5 minutes, or until the squash is tender. Transfer the vegetable mixture to a bowl with a spoon.
Squish the sausage meat from its casing into the same skillet. (Discard the casings.) Break the meat up with a wooden spoon. Cook the meat over medium heat for 3 to 5 minutes or until it loses its color. Add the meat to the vegetables. Add the cheese and stir. Set aside.
Cut avocado in half. Using a spoon, scrape the avocado from the skin into another bowl. Smash the avocado with a fork and season with salt and pepper.
Wrap the tortillas in moist paper towels. Heat in the microwave for 1 minute or until warm. Lay out the tortillas and divide the turkey mixture evenly on top. Top with lettuce and avocado, fold the tortillas over and serve with salsa.
From Food Network Kitchens