Preheat oven to 425 degrees. Line a rimmed baking sheet with parchment paper.
Remove the husks from your tomatillos. Rinse the tomatillos to remove the sticky residue, pat dry with a towel, and place on the parchment lined baking sheet. Rinse your remaining peppers, pat dry with a towel, and place them on the baking sheet with tomatillos.
Add your garlic cloves with the skins still on to avoid burning the cloves while they roast. Slice your half onion into fourths and add to the peppers and garlic. Drizzle the peppers and onions with olive oil and toss to combine. Roast on center rack for 40 to 50 minutes until onions soften and peppers begin to brown and blister. Cool slightly before removing stems and seeds from the poblanos, Anaheim peppers, and jalapeños. Remove garlic cloves from their skins. Take one of the poblanos and dice finely for your enchilada filling. Set aside. Lower your oven temp to 350 degrees.
With the exception of your tomatillos, give your peppers a rough chop and add to your blender. Add your tomatillos, onion, and peeled roasted garlic cloves. Add in 1 teaspoon kosher salt, ¼ teaspoon ground black pepper, oregano, cumin, and cilantro. Blend on low speed until well combined and smooth. If sauce is too thick, add a tablespoon or two or water at a time until your sauce is desired consistency—not too watery but not too thick. Pour into a nonstick skillet and keep warm on low heat while prepping the rest of your enchiladas.
Dice your roast chicken and set aside. In a separate nonstick skillet heat two tablespoons olive oil over medium heat. Dice your zucchini and onion and mince your garlic. Add your diced onion the skillet and season with a pinch of kosher salt and pepper. Sauté until translucent, about 3 to 5 minutes, then add your garlic and zucchini squash. Sauté the veggies until zucchini is softened, about 5 minutes. Add your corn and cook until warmed through and any liquid from frozen corn is evaporated, about 3 to 5 minutes. Remove from heat and add your diced chicken, the reserved diced poblano, and about a ¼ cup of your prepared enchilada sauce. Stir to combine everything together. Taste and adjust for seasoning with salt and pepper as desired. This is your enchilada filling.
Heat about 1 cup neutral oil in a medium skillet over medium-high heat. When the oil bubbles immediately when you touch the edge of a tortilla to the surface, it’s ready to fry your tortillas. Working with one at a time, fry the tortillas, turning once, about 10 to 20 seconds per side; the tortillas should still be pliable but slightly browned. Transfer your tortillas to the warmed enchilada sauce, about two or three at a time, to coat your tortillas in the sauce. Removed your prepared tortillas to a plate and work on saucing the rest of your tortillas.
Ladle a spoonful of sauce onto a baking dish for your enchiladas. This will help prevent some sticking while baking. Working with one tortilla at a time, spoon a couple tablespoons of filling on your tortilla, roll them up, and place them in your prepared baking dish. Repeat until all tortillas have been filled. Top your enchiladas with remaining sauce and sprinkle your cheese on top.
Bake for 20 to 25 minutes at 350 degrees until cheese is melty and golden and edges of enchiladas are crisp. Allow to sit 10 minutes to cool slightly before serving. Serve with chopped fresh cilantro, dollops of crema, and cotija, if desired.