Zidane isn't really the problem, the tactics are the same as last season. Injuries have played a big part in this but the biggest problem is the form of some of their midfield and defensive players. Isco is playing better than last season and both Benzema and Cristiano are about at the same level as last season.
Their fullbacks played a huge part in their attack and with Carvajal injured (with an 18 year old in his place), Marcelo out of form, combined with all of Casemiro, Modric and especially Kroos being subpar are leading to this. Ceballos, Llorente and Kovacic once he returns have to start challenging for those places.
They should have replaced Morata but the front 3 isn't the problem right now.