The term 'Zoo Heavyweight' refers to three large animals found in zoos: the HIPPO (5 letters), Rhino (5 letters), and Xmsqv (5 letters). The HIPPO is a large mammal native to Africa that can weigh up to 8, 000 pounds. The Rhino is a large mammal native to Africa and Asia that can weigh up to 6, 000 pounds. Xmsqv is a large mammal native to South America that can weigh up to 4, 000 pounds. All three of these animals are considered to be zoo heavyweights due to their size and weight.