If it's zebra pictures you want, then you won't be disappointed on an African safari. In Eastern Africa they occur in herds numbering in the thousands during the migration while in Southern Africa they are more spread out, but it's still possible to come across a large herds in certain places.
There is a mini migration of zebra in the Kruger National Park that occurs in the Lower Sabie area every year. I was dubious about this when I first heard about it but I've since seen it myself - a herd of over 100 zebra on the other side of the Sabie river while driving towards Skukuza.
These 'striped horses' are reputed to be a favored food for lions so it's maybe a good thing that there are so many of them around.
One of the advantages of photographing zebra is that they are so photogenic, you really have to struggle to get a really bad image of them. I always try to capture behavior as this makes the pics a lot more interesting than just an animal staring into the distance.They often have a tendency to stand next to each other top to tail so that they can whisk flies away from each others faces, or so the theory goes. They also roll in the dust to try and get rid of some of the parasites that cause their skin to itch and when they call out to each other it looks like they are grinning widely.
Any one of these behaviors can really liven up your photos so when you see a zebra on safari be sure to be on the lookout for them and keep your finger on the shutter.
You can take better wildlife photos in general on your safari by using the tips and guidelines in an e-book I've written about the subject. Get your free copy of "Better Safari Photography" for improved wildlife photography here..