Z-Bo was recently benched. The Grizz as we know them might be on their way out after an extremely underwhelming start to the season.
It's not a huge, sexy upgrade or anything, and Z-Bo isn't an ideal fit, but swapping Lee and Zeller for ZBo (and good 'ol Vinsanity as a throw-in), would give the team some added punch down low.
It might not make the Celts that much better in the regular season, but in the post-season having a guy like ZBo could make the difference in a first round playoff series. You need guys who can step up and score in tough spots. Think of it as adding an extra gear to your car that you only really need when you're trying to pass eighteen-wheelers on the freeway (a manuever I would never attempt in real-life).
Taking on ZBo and Vince would kill some of the team's cap space for next summer, but I'm not too concerned about that.