Bring water, rice, and chicken bouillon to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until the rice is tender and liquid is absorbed, 20 to 25 minutes.
Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Heat olive oil in a large skillet over medium heat; cook and stir zucchini, celery, and onion in hot oil until tender, about 5 minutes. Stir rice, cream of mushroom soup, cream of mushroom soup with roasted garlic, water chestnuts, chicken, mayonnaise, and lemon juice into vegetable mixture. Transfer mixture to prepared baking dish. Spread French-fried onions over rice mixture.
Bake in the preheated oven until bubbly and lightly browned, 30 to 35 minutes.
