The term 'Zoo Heavyweight, Briefly' is a crossword clue that can be solved with the answers 'HIPPO' and 'RHINO'. Hippos and rhinos are two of the largest animals in the world, and they are both found in zoos. Hippos are native to Africa and weigh up to 4, 500 kilograms, while rhinos are native to Asia and Africa and can weigh up to 3, 600 kilograms. Both animals are considered to be zoo heavyweights due to their large size.