ZBrush comes with a plugins folder located within the ZData folder. This folder is for factory-installed plugins, only, and should not be modified. Adding or removing files may cause unexpected behavior.
To correctly install user-created plugins which will be loaded at startup, you need to do the following:
Create a new subfolder within the ZStartup folder and name it “ZPlugs”
This only needs to be done once. From that point on, all user-created plugins which are placed within this ZPlugs folder will be automatically loaded at startup.
One more advantage of placint the plugins within the ZStartup folder is that they can easily be disabled. When you wish to start ZBrush without loading any user plugins (such as when debugging a plugin or resolving a possible plugin conflict), simply hold down the Shift key while launching ZBrush. If done correctly, you will see the following text at the ZBrush title screen: “User-customized plugins disabled.” This text indicates that in this ZBrush session the user-created plugins located in the ZStartup\ZPlugs folder have not been loaded automatically. They can still be loaded manually, however.