Isaiah describes what the world will be like when the king rules. There will be complete peace in the world. This is shown by the peace that there will be even among animals. Animals that normally kill other animals will not kill them, and they will all be safe together.
These phrases refer to these animals in general, not to a specific wolf or leopard. These are all strong animals that attack and eat other animals. Alternate translation: "Wolves ... leopards ... young lions" (See: [[rc://en/ta/man/translate/figs-genericnoun]])
The phrases refer to these animals in general, not to a specific lamb or goat. These are all animals that eat grass and straw. Other animals sometimes attack and eat them. Alternate translation: "lambs ... young goats ... calves ... fattened calves" (See: [[rc://en/ta/man/translate/figs-genericnoun]])
The phrase "will be" is understood. Alternate translation: "the calf, the lion, and the fattened calf will be together" (See: [[rc://en/ta/man/translate/figs-ellipsis]])