I found it on StackOverflow and it works ! If someone want to know how to do it, here it’s the code:
jQuery(document).ready(function($) {
$(window).load(function() {
$('.flexslider').flexslider({
animation: "slide",
controlNav: "thumbnails",
start: function (){
}
});
$(".flex-control-thumbs li img").hover(function(){
$(this).click();
});
});
});