Are they ZorroII memory boards? They should work, but only to a maximum of 8MB. And I don't think they'll be very fast. Better than nothing, though.
As for ZIPs,
Mr. Hardware sell some ZIP replacement chips. They're not original ZIPs, but a contemporary replacement for them. Don't know how well they work, but it's another option.
Your best bet is to find an accelerator that supports adding SIMMs.
