I think its a win/win for both.
Rangers needed to do something to shed some salary. Brassard is not at all on a decline and will see top line minutes in Ottawa. Zibanejad will likely get around the same money as Brassard on a new contract next year, if not more. Its a good move for the Rangers, but they're still stuck with Nash, Staal, and Girardi. Rangers could win in the long run depending on Zibanejad's further development and if he can maintain his output of last season, but I like the deal for Ottawa in the immediate.
May be a set up move by the Rangers for a bigger deal involving one of the albtrosses but its a step in the right direction although Brassard's departure impacts them immediately and Zibanejad is no guarantee to replace him completely.
There's no clear cut "winner" yet. There's positives and negatives for both teams, but I think there's more ifs for the Rangers espc with Zibanejad needing a new deal shortly.