Extending Web-Application

Is it possible to extend a web-application to use Windows authentication provider even if it has already been extended once before. I have created a new web application in SP 2010 which uses Windows & Claims and has already been extended once to use only claims authentication. Now I require to extend it once more to support CMIS framework.

1.Could you let me know how to configure/implement this?

1.Will there be any impact?