Chop zucchini/Mexican Gray Squash into bite-sized pieces. Set aside.
Add enough vegetable broth to line the bottom of sauté pan. Sauté zucchini for about 3 minutes or until it begins to soften. Watch the bottom of your pan so that the broth does not dry out or pan begin to stick. Add more broth if necessary.
Add the frozen mixed vegetables, black chili beans, onion and garlic powders. Do not drain the chili bean liquid/sauce from the can, but add it to the mixture.
Continue sautéing a few more minutes or until vegetables have softened and the flavors have mixed well. Set aside.
The Mashed Potato Layer
In a sauce pan, bring vegetable broth, vegan butter (if using) and plant milk to a gentle boil. Remove from heat.
Stir in dehydrated potato flakes and nutritional yeast. Add salt if desired.
Putting it All Together!
Layer and spread in a 9x13" pan in this order: 1/3 jar of salsa verde,2 1/2 tortillas - tear to fit and cover the salsa layer, 1/2 vegetable mixture, 2 1/2 tortillas - tear to fit and cover the vegetable layer,mashed potatoes - use all of the potatoes. Carefully spread over tortilla layer,1/3 jar of salsa verde,2 1/2 tortillas - tear to fit and cover the salsa layer,1/2 (remaining) vegetable mixture,2 1/2 tortillas - tear to fit and cover the vegetable layer,1/3 jar (remaining) salsa verde
Cover and bake at 350° for 30 minutes. Let sit for about 10 minutes before serving.