The memory will have a lower priority than the motherboard memory. So motherboard memory should be used first by the OS and then the Zorroram.
Although slower than MB ram and other Fast Slot connected memory it is still faster than MMU mapped swap ram like Gigaram did. Using it as swap space does not make much sense but using it as a RAM disk does.
If you were going to use it as just SWAP space why not just use it as RAM? I am sure the use of the programs to move data in and out of the ZorRam like swap memory should be even slower.
You could try making a RAM or RAD drive that only uses the ZorRam address space (not sure you can even do that) and then using Gigaram or other software that did virtual memory on OS3 to save the swap to the ZorRam RAM/RAD device. Might be very interesting but I doubt it would be faster than just using it normally.
You would need a MMU for the Gigaram style solution.