[tsukikakushi]

At the practice where I work, we use Purina E/N, it's a veterinary exclusive diet, and is pretty much just a bland diet. Z/D is more for animals w/ food allergies, which he may or may not have. the only way to test that is to try the food, no treats, etc. Is he just an indoor cat, or does he go in/out? He may be getting into things if he goes out. There's also a product called Fortiflora, it's pretty much like Activia for animals. There are other brands out there, but the Fortiflora is very palattable and most animals love it! Prescription diets can be expensive, but are definately worth it if the fix the problem! Good luck, I hope your kittty gets better.