There's plenty of things that we can attribute to the 3 game win streak.
Zeller as a starter provides consistency on both ends, albeit not as fluid offensively as KO. And of course the schedule is getting way easier.
I think my biggest reason is that Brad is relying more on the starters to drive the car, and giving less playing time to the bench. Don't get me wrong, bench depth's awesome.. but during November, it seems like we were playing platoon ball with the starters/bench playing similar minutes. Recently, it looks like Brad's giving the starters way more minutes. Phil Pressey's not getting his time while Rondo/Green are close to or over 30.
I'm all for it, let the starters ride. They have the experience to recover lost momentum in the 4th, and let them try to close games.