Thanks Zulf, Yes, it is resolved.
Sorry for not responding before. I was doing some comparison tests with Ridizain and Twenty Fourteen in order to understand the way it now works; I am using your plugin Fourteen Extended in both cases.
Now, in Ridizain, when hitting CTRL - a few times, the content gets smaller but the header image and the primary menu (top) remain as large as the screen (for example, I hit CRTL - 5 times before the header starts to shrink). At that point, the site looks a bit silly, the text of the content is very small while the header remains big.
In Twenty Fourteen, the header and the menu do shinks along the content, so the relation between the header text and the content text looks better.
Am I making sence? Maybe it was intentional that the header image remains that big. Was it? Since I use a large screen, I often use CTRL - to decrease the size of the font in the sites I visit, so I guess maybe other people do that too?