Citing ideas but extending information
It seems to me you should simply expand the text to provide the background that "Expert (cite year) has shown that A,B &amp; C are important and Smart (cite year) has shown that A, Y, and Z are important. Based on circumstances I postulate that also Red and Blue A are important along with B, C, X, Y, and Z". I hope you get the point? In other words describe the findings of Expert and Smart and then add your own "hypothesis" or ideaand make it clear that (a) it is your idea and (b) on what you base the idea. It is not clear fom th equestion whether it is a hypothesis to be tested or a result of your own research. Depending on which the way you present things will be slightly different, of course.