Puree first 5 ingredients in a blender to make a thick chile sauce. (Or, place these 5 ingredients in a 2 cup measuring cup and puree with an immersion blender.).
In the bottom of a 9x9 casserole dish, spread 1/2 cup of the red enchilada sauce, covering the whole bottom of the pan.
Layer 4 corn tortillas on top of sauce, overlapping slightly.
Pour 1/2 cup of the chile sauce over tortillas and spread evenly. Cover sauce with a third of the zucchini slices, a third of the pepper slices, and a third of the shredded chicken. Sprinkle with a handful of cheese.
Repeat to make two more layers. (First lay down more tortillas, then sauce, then toppings.).
Top final layer with 4 more tortillas. Top generously with red enchilada sauce and the remaining cheese.
Bake at 350 for 25-30 minutes, until cheese is brown and bubbly.
NOTE: I had some enchilada sauce and chile sauce left over, so I stirred it into a can of black beans, and simmered it on the stove while the enchiladas were in the oven. Turned out AMAZING.