The zebra represents the danger of passivity. If Pi chooses to simply sit and wait, circumstances (and predators) will tear him apart. Therefore, that is not an option for him. He can't just draw back and avoid the tiger. He must enter into an active struggle for dominance with it, contesting for mastery.
THey all repressent Pi's animal like characteristic
the zebra represts streangth and the will to survive even though the hyena was killing the zebra, he tryedv to stay alive. The zebra can also be an example of innocence or vulnerability it was what could have happened to pi if instinct hadnt taken over andthe will to survive hadnt been strong. its kill or be killed.
descent into savagery