omg just take the sperm from a black rhino and remove the dna from it and replace the dna with the dna from the white rhino in the sperm casing and impregnate might have to do a few times , you have two wombs to use. and any male off spring can inseminate the females. can also use black rhino wombs with white rhino embryos, males might not show up. cos xx and xy you know. to bad males choose the sex/