ZBR and ZTL document system in Z Brush

I started to create with ZSphere
I saved it both ZBR and ZTL cuz I was not sure which one is what for.

Then with pressing A and remeshing the poly group with 4 steps, I got this creature. I saved it also in ZBR and ZTL format.

When I started painting, my sister came and wanted to check her notifications on facebook! -_- And I forgot saving the tool. So BE CAREFUL! While working if you don't save the tool, you can't edit 3D model anymore. I got this info from polycount.com;

"Document (ZBR file format): Saves pixols, only! This format is meant for creating
illustrations. Any 3D data (if your model is in edit mode) is converted to
2.5D data when saving as a document. (Document > Save or Document > Open)

Tool (ZTL file format): Saves polygons. Use this format to save a model as 3D data that you
can continue to work with in edit mode later. This format will also save any maps that are
applied to your SubTools via the Tool palette. (Tool > Save As or Tool > Load Tool)

ZProject (ZPR file format): New to ZBrush 4 is a format that saves considerably more data
than the ZTL format does. This format will save the document settings including size and
lighting, all materials that are used, the model itself and even the size/position/rotation of the
model on the canvas, render settings, Timeline and more. In short, using this format allows
you to return to ZBrush exactly where you left off. Keep in mind that this also results in a
much larger file size than the ZTL or ZBR formats.
(File > Save As or File > Open)"

http://www.polycount.com/forum/archive/index.php/t-84983.html

At last; 

with some textures.