Would you throw in Giraffe and Eland.
Well, then go for the 8x68, 8mm Rem. Mag, 338 Win., 340 Wby,
or the .375 H&H, pick according how well you can shoot any of them.
For anything up to Zebra incl, the 30-06 probably do fine, or if you like, one of the .300 Mag. variations all with suitable bullets of course.

Remember, a well placed 06 bullet is a lot better then a poorly placed .375.

Picking any cartridge out of a suitable group seems like choosing women. Some hunters like short and squat ( .458 Win or .300 WSM) while others in our clan seem to prefer the tall slim looks ( .300 H&H or .375), yet others seek the tall husky teutonic variety women ( .470 or .5oo Jeffery). Hmmmmm...............