not going to happen,...... the hp z420/620/820 systems do not support booting from nvme they only support boot from SATA SSD
they will however access the nvme ssd as a data drive (win 7 needs special drivers) win 8 and up have builtin driver support
some people have used a special boot loader method to force a load of the missing nvme driver code before then xfering control back to the windows bootloader
google boot nvme on ami bios win raid as keywords if you wish to try this method