No, it wouldn't speed up the system, as RAM on Zorro is a bit slower than RAM on motherboard. And system will always prioritize the motherboard RAM over Zorro RAM. See these
results of bustest in A3000 with A3640 and ZorRAM.
Still, in my opinion ZorRAM or BigRamPlus are excellent additions if you don't want to buy a (much more expensive) turbo board. Just don't expect any performance improvement.