I bet it because the SCSI card requires Zorro II DMA which the ZIV board doesn't support.
The only way to get the GVP card working with the ZIV is to somehow disable the SCSI card's DMA support. Even if you do that you will find the transfer speeds horribly slow (like around 50Kb per second) as the CPU has to do the work, it is a similar situation to A2091 cards when installed in Amiga 4000D's due a hardware bug in the A4000.
If you were considering getting a SCSI CD burner etc. I'd suggest getting an IDE model unless you can find a SCSI card that works well without Zorro II DMA.
