Here's why:
* Different Species: Hippos and rhinos belong to entirely different families and orders. They are as distantly related as a cat and a bird.
* Genetic Incompatibility: Their genetic material is too different to be compatible. They have different numbers of chromosomes, and their reproductive systems are designed for specific species.
* Physical Differences: They are physically very different. Hippos are semi-aquatic mammals with thick skin, while rhinos are terrestrial mammals with thick, armored skin and horns.
In short, breeding a hippo and a rhino is biologically impossible.