Presumably, you mean a NASO tang (Naso lituratus) ? If so, you'll need a LARGE tank for one. They grow to be 18" in the wild, so you can figure on at least 12" in an aquarium.
How big IS your tank? You already have 3 zebrasoma tangs, which like the others have mentioned, is leading up to some heavy aggression, if it hasn't already started.
Otherwise, if the tank is large enough, (say..over 200 gallons) then the naso SHOULD be fine with your others, totally different body shape, different natural food sources, etc) I had one Naso in my 90 gallon for a long time, (yeah, I know, do as I say, not as I do, but it was waiting to go into my 180) and it got along fine with my purple and kole tangs. NEVER anything more than an occasional twitch of the tail at each other.