Hello,
thanks for your reply. I also asked this question to a specialized ram seller.
I got 32 gigs non-ECC ram at 1600mhz running now without problems, which isn't supported according to the manual, but it works like a charm.
Because I got a second HP Z210 with ECC ram I also tested the ECC with the I/ and this also works. So this information in the manual is also wrong.
Best regards,
Tobias