The old "glue-and-cut" symmetry of massless propagators, first established in Ref. [1], leads -after reduction to master integrals is performed -to a host of non-trivial relations between the latter. The relations constrain the master integrals so tightly that they all can be analytically expressed in terms of only few, essentially trivial, watermelon-like integrals. As a consequence we arrive at explicit analytical results for all master integrals appearing in the process of reduction of massless propagators at three and four loops. The transcendental structure of the results suggests a clean explanation of the well-known mystery of the absence of even zetas (ζ 2n ) in the Adler function and other similar functions essentially reducible to massless propagators. Once a reduction of massless propagators at five loops is available, our approach should be also applicable for explicitly performing the corresponding five-loop master integrals.1 The so-called Laporta approach [4-6] seems to be most often utilized but a few other promising methods are being now actively developed [7][8][9][10][11][12].2 At least well-established in practice. See below for an instructive particular example of a class of massless propagators and also [13,14] for an attempt to formalize the concept of the masters integrals and to prove the universality property in general. A related discussion could be found in [15][16][17][18].