Bale getting the treatment he's having doesn't have that much to do with Zidane: the frenchman is only pulling off what the crowd of Real Madrid want. They all want him out, and have, rightly or wrongly, blamed him for promising so much through many years (as potential Cristiano replacement) actually being quite good a times this season but ultimately falling way short.
Spanish fans get upset by many things you'd think are irrelevant in the PL: they demand players being very committed, almost to the point of it being a facade or plain show, in that players have to have sad worried faces on the bench at all times if their team is losing, have to celebrate everything that goes their way (also when on the bench), etc.
Bale has been injured, has blown hot an cold (in the specific context of not measuring against Cristiano, again due to maybe unfair expextations)... yet the killer thing has been that Spanish media and fans have fixated on him going home from the stadium before the final whistle (ergo, not showing "commitment"), him barely speaking a sentence of Spanish (also, apparently, proof of his lack of "commitment"), etc etc.
It has a lot to do with cultural issues: Agüero and Silva probably speak as much English as Bale can Spanish, but that is practically a non-issue on the UK as long as you do well on the pitch. The sideshow of showing all that spiel of commitment is demanded here mainly on the pitch, by running, getting stuck in or whatever.