I would be very interested to see any research that shows that Humulin N works for cats. I don't believe anyone here is familiar with any new research being done on it, but if you can get some documentation or some links from your vets, please share them. I don't believe there is any case of it working better than Lantus, Levemir or Prozinc with people or cats here, but I've only been around for a little over a year. Is there some new protocol for its use that we don't know about?
My cat was on compounded PZI for about 10 weeks before going into remission. The problem with compounded PZI is consistency of quality, so you have to make sure you get it from a reliable supplier. Mine was supplied by Veterinary Pharmacies of America (VPA) in Houston TX, but I don't believe they still sell it. The most common source is "BCP" which is also based in Texas.
Carl