In this paper, we demonstrated a high-efficiency mid-infrared ZnGeP2 (ZGP) OPG/OPA system, operating at the mJ-level with hundred-picosecond pulses. The ZGP-based OPG configuration achieved a maximum pulse energy of 1.06 mJ at a repetition rate of 1 kHz, utilizing a pump pulse energy of 2.59 mJ and operating at a central wavelength of 3.9 μm. The system achieved a maximum slope efficiency of 51.1 %, leading to a corresponding total optical-to-optical conversion efficiency (OOCE) of 40.9 % and an output threshold as low as 0.046 GW/cm2. However, the beam quality factor M2 deteriorated, reaching values above 45. To optimize the beam quality of the mid-infrared laser, we employed an OPG/OPA tandem configuration and a double-pass OPG configuration, resulting in maximum pulse energies of 0.85 mJ and 0.36 mJ, respectively. At the highest output energy, for the OPG/OPA tandem configuration, the beam quality factors M2 were measured to be 3.2 in the x direction and 2.7 in the y direction. For the double-pass OPG configuration, the beam quality factors M2 in the two directions were measured to be 3.5 and 3.2, respectively.