High-yield two-temperature synthesis and subsequent growth of ZnGeP2 crystals are investigated. By X-ray phase analysis it has been demonstrated that two-temperature synthesis of ZnGeP2 has been achieved using binary zinc and germanium phosphides formed at a Zn-Ge mixture temperature of about 900 degrees C and a P pressure of 7-10 atm, Using heat balance equation a ratio of thermal conductivities in solid and liquid ZnGeP2 near the melting point has been determined. The value of the determined ratio is K-L/K-S congruent to 2.3. Analysis of the most favorable crystallographic directions for ZnGeP2 growth has been performed. These directions are [1 1 6], [1 3 2], [1 1 0] and [1 0 2]. Data for optical absorption of as-grown and annealed ZnGeP2 crystals have also been presented and discussed.