The easiest way to work around the non-DMA issue is to use the buffer address mask (in HDPrep) to make sure the buffers are allocated within DMA memory. E.g. if the first 4 megs support DMA and 4+ meg not, you'd use a mask of 0x3ffffc. You'll need to find out where each expansion's memory is located at first.
Obviously it makes sense to fully use the Mtec's memory and reduce the 16 bit RAM to the needed limit (assuming the Mtec mem configures below the 'magic' 16 meg, so that it 'collides' with the Zorro II mem expansion).