Composition comprising a non-nitrogenous zinc salt and a particular cationic surfactant The present invention relates to a cosmetic composition comprising, in a cosmetically acceptable medium, at least one particular zinc salt and at least one cationic surfactant chosen from particular quaternary ammonium salts, in a specific weight ratio. Another subject of the invention relates to a process for treating keratin fibres, using such a composition, and to the use of such a composition, preferably in the form of a leave-on care product, for conditioning keratin fibres and protecting their artificial colour from fading.