I've many documents (all are images) opened within MDI, if user click
to zoom one image, how can i synchronize all other documents? to post
messages, or else? Thanks a lot for any idea.

Dear H,

I don't understand why you want to sync the zooming  of different images.
At any rate, a good place to start is CDocument::GetFirstViewPosition() and
GetNextView().

Help on GetNextView has a nice example. (You'll probably want to set some
variables for each view inside the loop as well or post a message now that
you have a pointer to the view.)

For all documents, you'll want CDocTemplate::GetFirstDocumentPosition() and
GetNextDocument() to get each document and then use the example loop for
each view.

You'll need to implement the document stuff for each different template you
want updated.

Hope this helps,

Fred

Take a look at SendMessageToDescendants()