Spray 13x9-inch (3-quart) glass baking dish with nonstick cooking spray. Brown ground beef in medium nonstick skillet over medium-high heat for 5 to 7 minutes or until thoroughly cooked, stirring frequently. Drain.
In medium bowl, combine tomatoes, zucchini, onions and beans; mix well. Stir in cooked ground beef. Reserve 1/3 cup enchilada sauce; set aside. In another medium bowl, combine remaining enchilada sauce, sour cream and taco seasoning mix.
Spoon 2 tablespoons enchilada sauce mixture in bottom of sprayed baking dish. Arrange 8 tortilla halves over sauce, overlapping as necessary. Spoon half of vegetable-bean mixture over tortillas. Sprinkle with 1/2 cup of the cheese. Spoon half of remaining sauce mixture over cheese. Repeat layers, reserving 1/2 cup cheese for top. Top with reserved 1/3 cup enchilada sauce. Cover with foil; refrigerate at least 8 hours or overnight.
Heat oven to 375°F. Bake casserole for 30 to 35 minutes or until thoroughly heated. Uncover; sprinkle with reserved 1/2 cup cheese. Bake, uncovered, an additional 5 minutes or until cheese is melted. Let stand 5 minutes before serving. Sprinkle with cilantro.