Zidane first played under Ancelotti when the Italian took charge of Juventus in 1999, with the Frenchman flourishing as a playmaker before making a then-world record 75 million euro move to join the Galacticos of Real in 2001.
Twelve years later, Ancelotti took the top job at Real, naming Zidane, who retired as a player after the 2006 World Cup, as one of his assistants ending the club's 12-year drought in Europe's elite competition, after which Zidane took charge of the reserve team.
Ancelotti was, though, given a brutal reminder of the short lifespan of Real coaches when he was sacked a year later after a season void of silverware.
Zidane took over the job, after Ancelotti’s replacement Rafa Benitez was sacked following seven months in the job, and won the Champions League the same season.
Having witnessed Ancelotti's sacking at the Bernabeu, Zidane is aware how ruthless the club's hierarchy can be. Even though Real sit three points clear at the top of La Liga with a game in hand, he said last Friday his long-term position at the club was far from safe.
"I'm not certain I'm going to continue here, not at all, and that's why I'm not preparing anything, I'm working for what I have left to do this season," he said.
"I know what it's like to coach Real Madrid for better or worse and I'm prepared for everything."
Zidane has been criticised in some quarters of the Spanish media for Real's stale style of play in spite of his achievements and his tactical nous was questioned after his side conceded an 85th minute equaliser to draw 1-1 with Atletico on Saturday.
Read the full article on eurosport.co.uk: Real legends Zidane and Ancelotti set for Champions League reunion