The main theme of the article is the analysis of the contribution of Milan Zloković within the field of proportions and modular coordination, the themes he has been dealing with during a thirty years long period. Particular emphasis has been placed on Zloković's mathematical-geometrical approach and methods as well as on the conclusions made by him based on the rich builder experience and the results of the detailed analyses in the search for the original proposal of application of the system of proportioning in architecture, preferential numbers and ideal design modules. In this article an attempt will be made also to clarify and bring closer the manner in which Zloković arrived to the conclusions that certain proportional systems were of greater significance for the architectural composition than some other ones and also in which manner they are applied in the designing process, independent of style. Finally, a wider survey of the manner in which Zloković stands out in respect to some of his contemporaries dealing with the same theme has been provided.