Deadman is right...I don't think there would be to big a risk with those two species. If anything, the problem may end up that the zebra's aren't aggressive enough to hold there own. Just depends on your group. Many think you cannot mix vics but that is not true...you just have to find the right mix which can be hard. If done properly and both species have plenty of their own females risk is pretty low. Now the sp 44's is a different story...They generally will spawn with anything so I would not mix those at all. Just make sure what you mix matches in aggression level and that your females are quite different. That is what makes it difficult.