First of all Zorro3 card are limited to 13.5 MByte/s, due to buster chip, so anything connected to zorro iii, slot will be limited to that speed.
https://en.wikipedia.org/wiki/Amiga_Zorro_IIIZorro2 is connected directly to the CPU, and on board bus, you can’t really clock up system bus, because it’s connected to all kind of custom chips that do not support high clock frequencies.
So the best way avoid this problem is to connect the graphic card directly to the accelerator, this way the accelerator, provide high speed bus access to the graphic card, while not messing up onboard timing.
