Okay. I have always used these settings in Zbrush but whenever I press the render button, with Keyshot set to external renderer, the groups get merged in a single mesh within Keyshot. I have to split the polygroup into subtool in order to apply different material in Keyshot. Preserving polygroups with their own material distinction, within Keyshot bridge mode would be super fast method. I'll ask on Zbrush forum too.