1. Preheat oven to 350°F(175°C). Shred the cooked chicken meat; set aside.
2. Bake the tortillas, turning once, until crisp, about 15 minutes.
3. Heat 1/3 of the oil in a saute pan. Add 1/4 of the onion and 1/4 of the garlic; saute until tender. Stir in tomato paste. Stir in water and jalapeÃ±o. Bring to a simmer, stirring constantly. Stir in chili powder and simmer until slightly thickened, about 10 minutes. Remove from the heat and stir in olives.
4. Heat the remaining oil in a saute pan. Add the remaining onion and remaining garlic and saute until tender. Stir in the green pepper and squash and saute 6 minutes. Stir in cilantro, cumin, and cayenne pepper.
5. Remove the pan from the heat and stir in chicken.
6. Coat a casserole dish with nonstick cooking spray. Place two of the tortillas in the bottom of the casserole dish.
7. Top with 1/2 of the vegetable mixture and then top with 1/2 of the cheese. Repeat and top with remaining tortillas.
8. Coat the top of the tortillas with a thin layer of the sauce; reserve remaining sauce. Place the casserole dish on a baking sheet and bake at 400°F(200°C) for 30 minutes.
9. Remove the casserole from the oven and allow to cool slightly. Place a serving plate upside down on top of the casserole dish; invert onto plate.
10. Cut casserole into quarters using a serated knife. Top with remaining sauce.