countzero's right: the A2386SX tries to allocate RAM space which is already used up by your 8 MB card. Different Z2 card not using RAM space but I/O space do not have that kind of problem (e.g. SCSI controllers w/o RAM).
Reduce the RAM on your Z2 RAM card to 6 or 4 MB to solve this problem. There's no other way to do it. Since you've got an accelerator card, you should populate and use its RAM instead - it's much faster anyway. ;-)