Temperment really depends on the exact species, I've seen up to 8 different species with that generic name. The two most commonly named 'zebra cichlid' I've seen are Metriaclima estherae & Metriaclima callainos. IMO, the two species I named would be about in the middle of the mbuna aggression scale (sounds official doesn't it ).
I was considering buying a full tank setup, apparently the guy had 5 zebra cichlids, 2 angels, 1 plec and some "tropical goldfish" , so I was wondering about them...
Doesn't matter now though, as I'm not going to buy it.