I'd say a slight lean toward Zidane and here's why:
1) He's really mastered the art of squad rotation unlike well, Luis Enrique. Granted Real Madrid is deeper but he wasn't afraid to rest Ronaldo towards the end of La Liga even when they needed points.
2) Wasn't afraid to sit Bale and James which probably had to make Florentino Perez cringe.
3) Hard to quantify this without being in the locker room, but he seems to be a great motivator. Just look at today, Real Madrid just ran Juventus off the park after halftime and he did a good job repairing the damage Benitez did last year.
4) He played Casemiro. A midfield of Modric, Kroos and James was never going to work well since none of them are true Dmids. With Casemiro doing the hard work (and somehow staying on the field at times) with Modric and Kroos, this is now the best midfield in the world.