Ancelotti was successful in Madrid, but his system was very different from that of Zidane. He frequently used Kroos as dm, which was very much part of the problem.
Zidane didnt radically change anything, but he introduced a proper DM from day1 and now he shifted towards isco in a free role and plays a very differently system. They also put much more emphasis on crossing the ball, which works great for them.
He isn't just following Carlos blueprint. Additionally he is making great use of the squad, which gives the team consistency and keeps everyone happy. We also know that real is a notoriously difficult place for a manager. Big egos everywhere. Zidane is doing a great job. That won't last forever but that's also just normal.