We report a novel and facile method to synthesize phase pure, chemically homogeneous, and highly crystalline CuInS2, an important element for optoelectronics, optics, and solar energy applications. This ternary semiconductor compound is grown by magnetic Zn doping under high-frequency magnetic induction at ambient conditions. The magnetic doping gives superparamagnetic heating of the resulting nanocrystals via magnetic induction, causing an accelerating growth rate of the doped CuInS2 under ambient conditions of 2-3 orders of magnitude faster than conventional autoclave synthesis. Shape evolution of the Zn doped CuInS2 nanocrystals from initially spherical, to pyramidal, cubic, and finally to a bar geometry, was detected as a function of time of exposure to magnetic induction. These newly-synthesized nanocrystals demonstrated considerably improved optical emission properties compared to those prepared via conventional autoclave methods. Nanostructural development of the nanocrystals was well characterized and a mechanism of crystal growth was proposed.