We have investigated the structural and compositional uniformity of a set of ZnSnP2/GaAs superlattices grown by gas-source molecular-beam epitaxy. Cross-sectional scanning tunneling microscopy reveals an asymmetry in interface abruptness, with the ZnSnP2 on GaAs interfaces apparently much smoother than the GaAs on ZnSnP2 interfaces. The increased roughness of the GaAs on ZnSnP2 interface occurs simultaneously with the apparent surface segregation of Sn. High-resolution x-ray diffraction and photoluminescence spectroscopy suggest that the ZnSnP2 regions consist of a mixture of ZnSnP2 and ZnSnAs2. This is further confirmed by cross-sectional scanning tunneling microscopy and spectroscopy, which reveal the presence of nanometer-scale ZnSnP2 and ZnSnAs2-rich regions. Interestingly, these lateral compositional variations are not correlated with observed growth front undulations.