If I look at the Zorro3 spec at serverftp it shows Zorro3 expansion space to be from $10000000 to $80000000, which looks to me like 1.792 MB of address space...
So my guess is that 7x ZorRAM will not work ;-)
Keep in mind, also, that the Mediator PCI can take upto 512MB of that address space. Other cards will take some of the address space too, such as a Deneb.
So in practise you'd be unlikely to get more than 4 ZorRAM cards at any one time. You can get 4 as has been demonstrated by AmigaKit, but there were no other cards in the machine at the time.
I am using two ZorRAM cards in my machine (128MB+256MB) and a Deneb, and a Mediator PCI taking up 512MB address space - enough for a Voodoo 3 or Radeon gfx card
