This tutorial describes a method which will enable you to transfer 3D-geometry (or UV coordinates) from one PolyMesh3D into another PolyMesh3D that is composed of an identical number of vertices.
In order to be able to apply texture to a 3D mesh, the mesh must first have properly-assigned UV coordinates. When UV-mapping a complex 3D mesh (such as those that can be created by ZSpheres), the standard UV mapping methods (Planar, cylindrical and such) are unable to generate UV-mapping without producing distortions and/or overlapping UV coordinates. Luckily, ZBrush’s AUVTiles mapping automatically solves this problem and eliminates the need to spend valuable time generating and adjusting UV coordinates.
At times, however, you may already have a texture that was created with a different UV mapping mode, and you wish to use the same mapping in order to have the texture fit the mesh properly.
See TVeyes’s thread for more information about this topic.
Example: We want to apply these textures…
…to this ZSphere tool…
Applying these textures to the mesh…
The texture is ‘broken’ into tiles and no longer resembles its original design. In some cases, you may be able to apply one of the standard UV mappings modes and get a satisfactory result, but in this case, the mesh geometry is too complex for standard UV mappings.
What we need is to simplify the mesh-geometry and then apply one of the standard UV mapping modes.
Unwrapping the ZSphere object to produce the following simpler shape…
…enables us to apply Cylindrical UV coordinates and get the following results…
…we then transfer the UV coords from the simpler object to the original mesh.
Here are the steps…
As shown above, we first need to unwrap the original ZSphere object to produce the simpler shape. This can be done by moving and rotating individual ZSpheres, or better yet, utilize the Linked-move mode to quickly align the ZSpheres.
First, we export the current geometry…
Generate a ZSphere-skin by pressing the “A” key and export the mesh as “TwistedMesh.obj” (by clicking the Tool 
Export button).
Next, draw the ZSphere tool on the canvas and enter Transform MOVE mode, press&hold the ALT key, click on a gray link and drag to ‘unwrap’ the ZSpheres-chain…
The simplified mesh is ready. Press the A key to generate its skin and export the mesh as “SimpleMesh.obj”.
The next step is to apply new UV coordinates to the simpler object and then replace the ‘simple’ mesh vertices with the vertices from the “Twisted” mesh. To do so, we will be making a use of ZBrush’s Morph feature…
Start by importing the ‘TwistedMesh.obj’, draw the mesh in canvas and enter Edit mode…
Select the texture to be mapped…
Before importing the next mesh we need to ‘protect’ the current geometry. we do so by storing its current vertices as a morph-target. Press the Tool Modifiers Morph StoreMT button…
Import the ‘simple’ geometry by pressing the “Tool:modifiers:Import” button and selecting the “SimpleMesh.obj”…
Note: We must use the “Tool modifiers import” button in order to import the mesh into the currently selected tool, The common Tool import button will create a new tool instead of using the current tool.
Apply the new UV mapping to the simple shape by pressing the Cylindrical (Uvc) button (you may choose any other best-fit mapping mode )
The texture is now properly mapped to the simpler shape…
The original ‘twisted’ geometry is restored by utilizing the MORPH deformation slider…
Applying morph at 100% …
note: The morph can also be used in less than 100% (or even negative) to gradually morph from one shape to another…
We now have the original (twisted) geometry with the modified (Simple) UV coords.
Here is a compact recap of the steps…
1. Create two 3D objects with an identical number of vertices.
2. Import the ‘complex’ mesh by pressing the Tool import
3. Press the Morph:store button
4. Import the ‘simple’ mesh by pressing the Tool Inventory import
5. Select a texture and apply best-fit mapping mode by utilizing the buttons in the Tool texture sub palette.
6. Apply Tool modifiers deformation morph at 100% (or simply press the Tool modifiers morph switch)
7. Continue to have fun ZBrushing 
Hope you’ll find this helpful,
-Pixolator
Thanks for explaining this! 
Never would have thought you could play around with morphing UV coordinates across models.
