Pep was coaching Barcelona B Team before becoming Barcelona's head coach, Zidane coached the Madrid's u23 Team, then he was Ancelotti's assistant, then after R.Benitez was dismissed, he became Madrid's head coach.
but remember one thing , Pep & Zidane and their major success leading 2 of the biggest teams in Europe without much of an experience, are the exceptions, the outliers, not norm. no other manager did what they did in recent history.