Smite removes Tryndamere and Zilean Ults

I was playing a game just 5 minutes before posting this thread and in the game a Warwick would use his smite on me (Zilean) or a Tryndamere on my team and the revive or the invulnerability would not work. If the Tryndamere had his ult going and Warwick would smite him then hit him, he would die. (Even if he had 3+ seconds left on it.) That also happened with me, when I would use my ult on somebody. Warwick could smite them and then kill them without my ult reviving them, or myself. (The results would persist if I ulted the Tryndamere whilst his ult was also going.) I'm not sure if this works for any person whom has smite or just Warwick. I am also not able to confirm if it works for any of the items that let you smite a enemy champion. The item that he had was the Skirmisher's Sabre - Devourer ( ) Please look into this and thank you for your time.

-KeensFate