Bring a large stockpot of salted water to a boil. Add the squash, return the water to a boil and cook for 3 minutes. Immediately drain the squash and run under cold water to stop the cooking. Set aside to drain.
Brown the hamburger meat in a large skillet. Add the diced onion and cook until the hamburger is not longer pink and the onion is tender. Place the burger in a large mixing bowl.
Add the cream of mushroom soup, the diced tomatoes with green chilies, the shredded cheddar cheese and the two beaten eggs. Stir until everything is combined.
Add the squash to the bowl. Gently stir until the squash is evenly incorporated throughout the mixture.
Place the squash mixture in one large 9 x 12 x 2-inch casserole dish or two 8 x 8 x 2-inch casserole dishes. At this point, the squash can be covered with aluminum foil and stored in the fridge for up to 24 hours or frozen.
Preheat the oven to 350 degrees.
Sprinkle the crushed crackers over the top of the casserole.
Bake for 20-30 minutes until the casserole is bubbling and the cracker crust is golden brown. If using frozen squash, you may need to allow the casserole to bake for and extra 10-15 minutes. Allow casserole to rest for 10 minutes before serving.