How to save the work file.If my work isn't finished when I export DAZ model to Zbrush?

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If my work isn't finished when I export DAZ model to Zbrush by Goz,How to save the file,so that I can go on the work next time?

if I export the model back to DAZ,and save as a .duf file.when I open the file ,then export the model to Zbrush next time, I can't find the layer data in the Zbrush.

Where did I go wrong？？？