As far as I'm aware, no you can't.
They both require specified drivers and they don't talk to eachother. You 'might' be able to run them at the same time but not in some sort of SLI/CrossFire style configuration. If you can do that then it would seem slightly pointless to me.
That has never been issue on Amiga. It's "always" been possible to use different type gfx cards simultaneous. I've used Voodoo3 on PCI and CV64/3D on Zorro together as well as three PicassoIV:s in same computer.
Usage can be for example for normal multidisplay home use (web and desktop separated etc), or demonstration situations where you need separate display for the audience and control display for yourself (done that at demoparties). Or if you can get cloned output it can be useful for software presentations (done that with MorphOS presentations).
