I am surprised you didn't find my review on the web of the Z9+.
There is so much potential with these machines, yet HP ran away from them never resolving issues.
I still have one as I was not able to sell it. I should have insisted that they try to fix the calibration and profiling issues under warranty. I didn't and left it off line for an extended period. My fault. These printers MUST be left on, as the daily maintenance ( CRON tasks) must be performed. IF not all the heads will show far beyond expected life. I replaced one that was no longer working, with a new one from HP. That was defective from the start, and cost me a lot of ink, and paper. Replaced with another, yet it reached far beyond expected life quickly. I am sure the reason is the other heads, they all work together.
So now the output no matter what the calibration or hand made profile in colour are biased with a bad magenta tint for skin tones. So I have this big beautiful printer that is only capable of greyscale prints.
While I loved the Z3200 for its total control on colour and adaptability to 3rd party media, the Z6 Z9 I cannot recommend for individuals, only for installations where an extended warranty is in place, and the machines can be left on 24/7. In Paris Picto labs have the Z9+ and it is perfectly suited to high production, equal to the Epson series.