Preheat the oven to 375°F (190°C).
Heat olive oil in a large skillet over medium heat.
Add diced onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet, breaking it up with a spoon, and cook until browned and cooked through, about 6-8 minutes.
Stir in ground cumin, chili powder, smoked paprika, salt, and black pepper. Cook for 1 minute to toast the spices.
Remove skillet from heat and stir in diced tomatoes and thawed corn.
In a large mixing bowl, combine sliced zucchini and yellow squash.
Add the cooked ground beef mixture to the bowl with the squash and gently toss to combine.
Lightly grease a 9×13 inch casserole dish.
Spread half of the squash and beef mixture evenly in the casserole dish.
Sprinkle half of the shredded cheddar and Monterey Jack cheeses over the layer.
Add the remaining squash and beef mixture on top and spread evenly.
Top with the remaining shredded cheeses.
Cover the casserole dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, until the cheese is melted and bubbly and the squash is tender.
Remove from the oven and let the casserole rest for 5 minutes.
Sprinkle chopped fresh cilantro over the top before serving.