Zone System to work in RGB scale
Zone System can be imroved by adding RGB space and the same value manipulation algorithm as of the Exposure module.
Currently module works in Lab color space only and does not produce reslistic colors.
As discussed here https://discuss.pixls.us/t/do-exposure-and-zone-system-use-the-same-algorithm/12535/6
Zone System renders results different from exposure, however both modules are intended to manipulte exposure values of pixels.