For me, the difference is that all these truly great coaches gave something new to football - a different philosophy and another dimension.
If you look at Guardiola, Klopp or Mourinho - they all have unique styles. Even coaches like Simeone, to another extent.
I agree with you. Guardiola has tiki-taka, Mourinho has double-bus and counter-attack (I am sorry I don't know how to call it), Klopp has gegenpressing. Simeone has same philosophy as Mourinho but he makes his reputation and career in Atletico when the club was in trouble, he built the club from very low start.
Zidane did not do that. He just won a lot of trophies with the most expensive football team in the world. Still too early for me to call him a great manager, although his results cannot be denied.
Zidane took the coach position in Madrid when the team is in best ages. Again I agree that he does not show his clear vision for his management philosophy. He is kind of a mix of many styles and the biggest success he does is manage the players and avoid conflicts with them. The exception is Bale and I see Zidane and Madrid behaved very bad with Bale.
Without Bale, Madrid could have one less Champions League and their club's Hall room.