The effects of the Y2O3 and Yb2O3 co-doping impurities on the transport characteristics and stabilization of the cubic phase in solid solutions based on ZrO2–Sc2O3 were compared. The crystals of the (ZrO2)0.99 –x(Sc2O3)x(Yb2O3)0.01 and (ZrO2)0.99 –x(Sc2O3)x(Y2O3)0.01 (x = 0.08–0.10) solid solutions were grown by directed crystallization of the melt in a cold container. The high-temperature cubic phase was stabilized at a total concentration of stabilizing oxides of 11 mol % for (ZrO2)0.99 –x(Sc2O3)x(Y2O3)0.01 crystals and at 10 mol % for (ZrO2)0.99 –x(Sc2O3)x(Yb2O3)0.01 crystals. At (9–10) mol % scandium oxide, the high-temperature conductivity of the crystals co-doped with ytterbium oxide was higher than in the case of the crystals co-doped with yttrium oxide. The (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01 crystals have maximum conductivity over the whole temperature range.