Except to be one of the nostalgic calibers of old Africa
@Franko If you want to stick with CZ, go with one of their standard calibers. Sounds to me like you are going to want a 416 Rigby.
I was just on a water buff hunt in the NT and borrowed rifles. The outfitter had 375's and an open sighted 458 win mag. After many shots on the first buff with the 375 and finishing him with the 458, I just used the open sighted 458 for the next 3 bulls.
However the issue was not the caliber, but the Federal blue box 270 grain ammo that just would not penetrate. The outfitter was saving money by having clients use 6 or 7 shots of $100/box ammo rather than buying premium ammo for $190 and taking a buff with one, two, or maybe 3 shots..... It takes penetration.