In a large skillet, heat oil over a medium-high flame. Saute onions, zucchini and bell peppers along with taco seasoning. Cook it for 2-3 minutes. Do not over cook as they are going to cook while baking.

Turn off the flame. Add black beans and corn to it. Mix it properly.

Preheat the oven at 375°F . Prepare the assembly line with fajitas, shredded cheese, enchilada sauce and tortillas.

Roughly divide sauce and fajitas into 2.Cheese and tortillas into 3.

In a 9x13 casserole pan, put some spoons of enchilada sauce at the bottom. Lay 3 tortillas over it(overlapping is fine). 

Spread a layer of fajitas and cheese over it and pour some sauce on it.

Repeat the layering process by placing 3 tortillas followed by layer of cheese, fajitas and enchilada sauce.

Place last layer of 3 tortilla and top it with cheese.

Cover the pan with foil and bake it for 30 minutes. Remove the foil and cook it for 10 more minutes.

Let it sit for 10-15 minutes. Cut into desirable size pieces. 

Serve it with some Guacamole and sour cream.