How powerful would this devil fruit be in comparison to mythical zoans like seiryu?

Mythical zoan, giant Nemean lion, the user turns into the nemean lion of greek mythology, a beast with impenetrable skin and tough insides, giant impervious claws and teeth. The user would be completely impervious to poisons that go through skin or burns or outside damage. The nemean lions roar induces fear and submission. The nemean lion in mythology was only killed by being choked to death by the legendary hero. Im thinking it would be up there with kaidos devil fruit considering you basically need internal destruction to fight it.