If you are hunting in Zim and the shots will be closer I would think your choice of a fixed 4 or 6 would work fine--if you are buying a variable I would go with a 2.5 to 8 or 3 to 9 or even the 3.5 to 10 which would work perfectly fine even in longer shots in Namibia--

One the plains game hunts I have done I used a 4.5 to 14 --shot excess of 50 plus animals with no problems what so ever... if I went back that is my "go to gun" and would probably use it again..

Make sure it is good quality glass--all the new higher end scopes seem to hold up pretty well.. personally I like Leupold, Swarovski and Schmidt/Bender...those would be my only choices..

Good luck---this is all part of the experience and makes it all that much more enjoyable..

Ripp