You didn't say which Panasonic 60" plasma he's trying to replace.
That's a large variance in picture quality, as Panasonic had some cheap POS models that even a Vizio these days could equal now. But they also had some top models that would be hard to beat in picture quality to this day (minus viewing 4K HDR content).

If the Z9 is out of budget, then I would certainly push for one of the 9 series.
The 850 looks OK; but if he had a top-of-the-line Panasonic from the last batch (i.e. TC-P65ZT60), then he might be disappointed. Because that would be a hard one to beat.