It's an EZ Flash IV, not a 3-in-1. They're two totally different carts - one with the full capabilities of a slot-2 cart while the other is merely an expansion cart.
From what I know though you should be able to use a EZ Flash IV together with an Acekard. And if that menu you speak of is what I think it is then it's completely natural for it to be there. All you need to do then is to patch all your GBA games properly with the EZ4 Client and copy them across to your EZ Flash IV and then launch the roms from that menu. That or you could use Exploader to load the roms off your Acekard.