I am now running the Kingston Predator M.2 PCIe card as my boot drive in one of my W7Pro64 Z600 workstations, and it is running great. I also did some testing and got that up and running in one of my xw6400 and xw6600 workstations. Have not yet tried it on a spare xw4600 but have no reason to believe it will not work in that too. The Z800 works this way just like the Z600.
I'll post more when I get more time. HP has two storage controller drivers listed for the ZX00 series and the more recent one (11.5.4.1001) did not work when I updated to that, so stick with the original (9.6.0.1014). Blue screen the instant boot went beyond BIOS. Also, my Acronis clone software would not clone over correctly until I changed image capture type to sector by sector. I used DiskPart to clear the Predator before doing the clone. Breakthrough came from a clean install, from scratch, so I knew then that it could work and then I worked my way back to the two tricks above.
It is very fast, and stable. For those who pay attention to such things: This upgrade is not like we experienced going from HDD to SSD. The feel is more like an upgrade from a moderate to a very fast video card. Noticable jump in speed, for sure, and well worth it.
You want to place that in a PCIe slot that is generation 2 or higher, and has at least x4 lanes. For my particular Z600 (my main home office workstation) I have a HP "2x2" Texas Instruments chipset USB3 card up in the top PCIe slot that would work for this, so I put the Predator card down in the lower PCIe x16 slot you'd normally think of as for a second video card. For those with xw6400 workstations there are zero PCIe Gen 2 slots so you'll run at 1/2 speed. For the xw6600 and xw4600 the two PCIe x16 slots are Gen 2 so use the lower of those for this card. You can look up the PCIe slot type posiitons of your ZX00 workstations in the technical and service manual. The Predator is a PCIe Gen 2 card that can run through 4 PCIe lanes so you want to at least give it that.
The ZX00 series are SATA generation II workstations, and this is one way to break through the speed limits of that. I'm using the Predator as my boot/applications drive, and just put in a nice enterprise grade 500 GB Samsung SSD as my "documents" drive. That combo is very fast.
The HP Z Turbo M.2 cards are two types: the G1 has an AHCI type of controller and the G2 has a NVMe type. You might have a shot at getting the G1 to work on the ZX00 series workstations but I don't think anyone will ever get the G2 to work in those because of the chipset and BIOS limitations of the ZX00.
The Predator M.2 PCIe card has an AHCI type of controller, and is proven to work so I'm advising my need-for-speed friends to go for that now in their ZX00 and xw6600/xw8600 and xw4600 HP workstations.