They screwed up their own country, then ran to South Africa, committing another crime of 'invading' it by not going through the proper channels. Corruption is rife in both countries, and as you say, how could that many have gotten in without bribing border officials. It's possible that there's a syndicate in Zimbabwe that fakes the paperwork for them, and that can be done with the assistance of just a few corrupt SA Home Affairs officials. Corruption have plagued that department for 20+ years, at the expense of ordinary South Africans. And let's not forget the biggest junk of all, Nigerians. The most crooked, immoral, corrupt, dishonest people on this planet, and the mental illness religion made them so.