I've two cards for my Z1.
But with K2100M the system didn't starting even in the safe mode 
Resp. this isn't drivers problem. Btw - these moves has been also - ineffectually
Moreover - i found vbios for HP and for Dell 2100M cards (in case with quadro was the same moments - any driver updates i've some time for adding few symbols to the *.inf driver file)
I, and I think many other people have wanted a system with a GTX and Quadro. But, I never saw a post that it works.
Actually - not for me, but anyway - this experience should be OK for those who need two cards