Hi Karen, I do recall hearing about this, but I don’t have many patients on z/d. Our own hospital cat developed some issues after being on it for awhile, though he ended up needing actual medication for his IBD which improved things a lot and I’m not sure if it was only diet related or not.
Other options include Royal Canin HP, which is what my own cat eats. There is no canned food version, so I use the Royal Canin Select Protein rabbit and pea. There is also duck and potato. Purina has HA for which I think there is also only a dry food option. Blue has HF, which comes in both dry and canned.
It can be a matter of palatability particular to each cat. My own cat did not like z/d to begin with but took to HP very well. There can also be digestibility issues particular to each cat that is unrelated to the hypoallergenic nature of the diet, not unlike your experience with z/d. A colleague’s cat developed diarrhea with the rabbit and pea canned food, while my own cats have no problem with it.
A slow transition is very important. For cats with food sensitivities I especially advise a good 1-2 week transition, which I did with my own. That way, if you start to see emerging issues with increased proportions of the new diet, you can make adjustments.