What they need to do is determine the ideal size of the herd, and sell enough hunting licenses for big bucks to keep the herd that size. Then use the money to keep up the park and stop poachers. But this is Mugabe’s commie hellhole, so fat chance.
That is going to hurt tourism and by damaging the tourist industry through culls and baby captures (selling to China) they and the general economy will lose more money than they will gain. Some do need to be sold responsibly and the money used for contraception programs.