This paper presents the findings of investigation of the elliptic flows of π0 mesons as functions of transverse momentum for different centrality classes of relativistic nuclei Cu + Au collisions at an energy of 200 GeV and U + U collisions at 193 GeV. A comparison of the obtained values is also presented. The results of the comparison have been indicated that a larger volume of quark-gluon plasma formed in the U + U collisions. Moreover, the elliptic flows of π0 mesons were established to have positive values at transverse momenta up to 10 GeV/c in the collision systems under study. Thus, the results obtained on elliptic flows allow us to further study the dependences of parton energy losses on their path lengths in the quark-gluon plasma forming in the Cu + Au and U + U collisions.