Pure rs-ZnO formed at 7.7 GPa and 2000 K in multianvil experiments (e.g. sample # 1) is shown in Fig. . These p-T conditions allowed us to ensure the completeness of the w-ZnO  rs-ZnO phase transition and to avoid ZnO melting. The synchrotron powder X-ray diffraction pattern (Fig. ) has shown that the recovered sample is single phase with no trace of w-ZnO. Refinement of lattice parameters and phase composition was performed using the structureless Le Bail profile analysis (FullProf software). The resulting lattice parameters were a = 4.2771(6) Å for rs-ZnO and a = 3.6195(7) Å for cBN, which are in good agreement with literature values. The coherent scattering domains of rs-ZnO are of ~62( ) nm with a lattice strain of 0.28(2)% according to the Williamson-Hall method (Fig. ), which is in good agreement with the TEM observations (Fig. ) of individual visible rs-ZnO grains (according to SAED, Fig. ), whose dimensions vary from 50 to 150 nm. It should be noted that long exposure of rs-ZnO grains to electron beam leads to reverse transition to w-ZnO.