I have a action button in Case object view page that render visualforce page on click? I would like to redirect it back from visualforce page to case object view page then to Merge screen How can I do this?

I did use below syntax:

   PageReference nextPage = new PageReference('/' + caseId); 

            nextPage.setRedirect(true);

return nextPage;

to redirect back to View page which works fine.

Mine question is How can I then redirect to Merge Case standard screen?

FYI: I tried below:

 PageReference nextPage = new PageReference('/' + caseId); //new PageReference(referrer); 

            nextPage.setRedirect(true);

              // Redirect to the standard Merge Case screen

            PageReference mergeCasesPage = new PageReference('/merge/CaseMerge.jsp');

            mergeCasesPage.setRedirect(true);

              nextPage.getHeaders().put('X-XSS-Protection', '0'); // Allow JavaScript execution

             nextPage.getParameters().put('nexturl', mergeCasesPage.getUrl());

return nextpage;

but couldn't achieve what I want. When I tried mergeCasesPage only then It  says url no longer exist or something .

I this is any way not possible can you please state reason.

@Iman Maghroori