Video covers how to import in two different stl files then use one of the stl files to cut the other mesh. The process depicted uses the live boolean system inside of ZBrush. The ZCnc plugin mentioned in the video can be downloaded from the Pixologic resource center:
https://pixologic.com/zbrush/downloadcenter/zplugins/

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These videos are not designed to be advanced tutorials, but rather to answer precise technical questions.