In 1972 Zhāng Kūn's factory released another modulated zheng, this one called Model 72. It had a somewhat flatter soundboard which made it easier to play, and featured a simpler modulating mechanism.
in 1974 Yingkou Musical Instrument Factory releases another modulated zheng, this one providing buttons for the performer to press rather than levers to move as had been the case in earlier models. It was lighter than previous modulating zhengs, but was still heavier than the soon-to-be ubiquitous Dunhuang guzheng.
Image: Dr. Han's Yinkou modulated zheng. Source: Han 2013