It really would not hurt if the Monarto Safari Park, Western Plains Zoo and the Werribee Park Zoo (even some of the NZ zoos) imported "just one" Grants Zebra stallion each every five years, It won't break the bank of these "major" zoos, but they would rather waste the money in other areas just plastic supermarkets and the like!
Also to add is that Australia Zoo has its African Savannah exhibit which is down to just 2 Zebras currently in what is one of their major exhibits for the zoo with a limited amount of African species anyway. Perhaps a import of even a small number ect 1.3 would put them in a good position now and in the future and be able to swap animals with other holders in the future!
It’d taken even less effort than that. Grant’s zebra can live (and breed into their 20’s), so all the open range zoos would need to do is import 1.2 Grant’s zebra and retain all female offspring. Foals are produced at 12 month intervals, so within five years, they’d have a herd size of at least eight mares and fillies. They could then swap the stallion out, with a new stallion heading up a herd of founder and first generation mares.
Following the acquisition of those four founder animals, a new stallion would be required every 10-15 years for genetic reasons (over representation).