I want to save all my zbrush work to a project file, then load the project file later and resume right where I left off. Can Zbrush do this? Typically in most programs you would do: File--> Save As--> ProjectName Then to load your project you would do: File--> Load --> ProjectName How do I do this in Zbrush?
When you crop/resize the document, ZBrush quits the 3D mode and goes 2.5D. Press "ctrl+n" to clear the canvas, drag your 3D tool again, press "t" to re-enter the edit mode (3D mode). One more thing: when you save the project with "ctrl+s", the document size should have been saved too (ONLY for that project).