My ZPR is now 1.2 Gb. Its getting slow. I have one tool with 25 subtools. I would like to split it in some way. I would like to put some subtools in another tool or move them off to another ZPR without losing the Subdivs if possible. Is this possible?
Thank you lots!
If you are saving undo history, they can get quite large, it can be deleted or not loaded when the file is opened.
As far as I know there are no undos when I open the file… As in after saving it and reopening it previous undos are lost… Though if you mean undos related to specific sub tools while working on them… Yes they stay as long as I am working… I will start deleting it regularly from now on… Thanks for the info… 
though I would very much like to spilt this cake(coz file is too monotone) 
Saving at lowest subdivision level is recommended. Use ZRemesher to get poly count down where possible. If it’s due to items in the Tool pallette, there’s this http://www.zbrushcentral.com/showthread.php?176896-How-to-clean-the-excess-3D-Meshes-in-the-tool-palette-Answered&p=1011378&viewfull=1#post1011378
deleting subtools from a project is simple.
just duplicate your file, delete the parts you don’t need from each subtool. You can then merge them back together when you’re done using subtool master and saving out a .ztl file.