French ex-president Sarkozy begins jail sentence

So is this a criminal president receiving justice, or a politically motivated prosecution?

A bit of both, there's no doubt he's more than guilty.

But it is also clear that judges (who are notable left-leaning, if not far-left) are much more efficient at prosecuting right-wing figures (Fillon, for 0 reason this time).

The "Red judge myth"is, well, a myth. And Fillon's case was very clear and he had all the reason to be prosecuted.

No it's not. A majority of judges belong the the "Syndicat de la Magistrature", a communist-leaning organization (https://fr.wikipedia.org/wiki/Syndicat_de_la_magistrature) which even participates (despite the supposed "independance" it should abide by) to the Communist Party's annual conference ("Fete de l'Huma"). COMMUNIST, not "socialist". Furthermore, many organizations and known figures of the french magistrature have regularly explained how they view there job as having a political mission, particularly, "avoiding prison", etc, etc... rather than enforcing the law.

Your own link said it 33%, so not the majority. A union has no obligation of "independence". Being member of a union does not mean you agree with everything, just that you think it's the best to defend your interests. The "Fête de l’Huma" is not the Communist Party's annual conference but it is indeed left leaning. There is no need to write communist in all caps, it's not an insult. For your last point you'll need to provide sources.