I would stay away from the Z/D canned. It's an extremely poor quality food with a ridiculous price-tag. Here are the main ingredients:
Hydrolyzed Chicken Liver, Water, Corn Starch, Soybean Oil, Powdered Cellulose,
No muscle meat, only organ meat. Corn starch??? Come on. And that powdered cellulose is basically sawdust. For a canned food, this one has a stupidly high amount of carbs (34% from calories).
Good luck convincing a cat to eat this for any length of time.
As well, I don't personally see IBD here, I see a constipated cat that needs to eat quality wet food. IBD is an extremely difficult diagnosis to make, even with a biopsy. Unfortunately vets tend to throw the term around far too liberally when they don't have anything else to offer up.
Glad to hear that Mr. Miyagi is home and doing better. Perhaps if you kept a log-book (
) that kept track of his pooping habits (like the size, frequency, texture), it could help you notice if something goes off before it gets serious.