Ironically, we ran out of ZD food recently, so I've been giving her the other guys' food - which, at the moment, is something called Solid Gold Katz-N-Flocken. It's one of the least expensive I could find where the primary ingredient was actually some variety of meat, not corn/rice meal. And, just like Fireball's, her fur got SOFT. Dr. F gave me strict instructions to keep her on nothing but ZD, but I was so sick the few days after I took her in that I couldn't get more (and they were out of stock while I was there). It certainly doesn't seem to have hurt, and if her fur's this silky-soft, it can't be bad for her skin, right?
She spent ten minutes this morning laying (not perching, with her pointy, pointy feet) on my chest, purring like a snugglebug while I scratched her head and face. Now, if only we can convince her not to SCREAM whenever she sees another cat, we'll be set.