How do the Death Ward spell and the half-orc’s Relentless Endurance racial trait interact?


What happens when you cast Death Ward on a half-orc? Do the effects of the spell and the half-orc’s Relentless Endurance racial trait stack?

If so, and you get reduced to 0 HP more than once, can you go back up to 1 HP a second time? Or does only one of them take effect and you can only be brought back to 1 HP once?

My DM thinks the latter.