Slideshow showing 3 slides (prev - active - next)
Edit2:

I found the solution by studying the flexslider module. You can manipulate sliders by #ID with the following commands:

(function ($) {
$(document).ready(function(){
$(".page-about-livio #flexslider-2 .flex-next").click(function() {
    $('#flexslider-1').flexslider("next");  //Go to next slide
    $('#flexslider-3').flexslider("next");
});
$(".page-about-livio #flexslider-2 .flex-prev").click(function() {
    $('#flexslider-1').flexslider("prev");  //Go to next slide
    $('#flexslider-3').flexslider("prev");
});
});
})(jQuery);