FredericoAsc, I'd say treating mathematicians as analogous to composers is slanted way too far over to the cognitive (i.e. intellectual) part of human mentation. Are you not neglecting the crucial importance that the - largely unconscious - intuitive, experiential part has in the mentation of composers? (In the interests of brevity I deliberately omit here the matter of feelings, affect and emotion, which of course bears huge and essential relevance to this topic but must wait for another time.)
If we're talking exclusively of the intellect in typical humans, I've long considered the limit of complexity it can tackle at any one moment to be pretty much commensurate with thinking - unaided - about the design and functionality of a steam engine. No amount of theory or methodological techniques can alter that substantially; it's just how we're built. The intellect is a relatively small and quite starkly bounded part of the human central nervous system, notwithstanding the huge degrees of aggrandizement - sometimes to absurd and even pathological extents - bestowed on the intellect during the modern era in some western cultures.
Or, to get more up to date, consider the fact that software programmers have long been encouraged to structure their code as "modules" such that each module contains only "a headfull of code"; which is still a sound, wise and valid methodological policy, despite the many development techniques and tools available now.
Sure, with long practice, some people manage to enlarge the scope of their intellect; but never to the extent that it alone can enable one to tackle the formidably broad and deep kinds of complexities that our intuitive and experiential faculties, working closely together with the intellect, enable us to tackle.
I speak as a systems engineer, now retired. A friend and colleage of mine, a highly adept mathematician and manager of the mathematical modelling group in the systems & software division where we worked together, used to say often, "systems engineering is a state of mind". And I would add, "systems engineers don't pop up overnight - it takes years." I believe something very similar applies to composers.
Nowadays, alas, It seems that not everyone can become a systems engineer, or a composer, or an architect, etc.. I believe it's partly of course a matter of being endowed with intellectual and intuitive faculties that have learned to cooperate fully and intimately with each other. But moreover, in our various cultures and subcultures today, achieving this state of mind seems to be somewhat elusive, given the marked sociocultural polarisations we now have between "Confucian" and Taoist", or "Protestant and Catholic", or "left and right", habits of mentation. Composers cannot be either-or; they espouse both "sides".
I've watched online and wholly enjoyed recent concerts given by Berliner Phil. and Wiener Phil. in which Williams was guest conductor for some of his works. Watching the musicians in the world's two finest orchestras play his "Imperial March", I could see they were unreservedly "into" the music, treating it as seriously and wholeheartedly as they do with any other great piece in today's orchestral repertoires.
I believe it's safe to say that Williams, who currently has works listed in 23 of Berliner Phil's archive of recorded concerts, is now counted by the leading musical coteries in Europe as one of the world's great composers. Zimmer, on the other hand, despite all his modern technological acumen and equipment (not to mention his abundant skills in self-promotion), has not been accorded that honour.