For the most part nearly all mbuna are compatible with each other (with some exceptions, for example you wouldn't want to keep mildly aggressive mbuna which resemble another species with high conspecific aggressive tendencies, etc).
I keep my red zebras and yellow labs with various pseudotropheus, labidochromis and metriaclima species. The red zebras will attempt to dominate the tank, and if they can do it with little or no opposition, they're fairly non-trouble makers afterwards.
They CAN be brutal against opposition, however and have the potential to become bullies in inadequate set ups.