They should work but it would be better to have a larger tank(what size do you have?) if your mixing mbuna with different agresive levels (labs have a low temperment-for mbuna, while zebras which specis do you have? are usually moderate)
But there are really too many species to tell you, so take a look around the internet heres a site with a few species, look around at your local stores, see what you like and post back on here with some specific names we should be able to tell you if what you find is compatible
