.block { width:100%; height: auto;  }
.zoom { 
    width:100% !important; 
    height: auto; 
    display:block; 
    position:relative; 
}

    .zoom img { display:none }

        .zoomOverlay {
            position:absolute;
            top:0; left:0;
            bottom:0; right:0;
            display:none;
            background-image:url(../images/zoom.png);
            background-repeat:no-repeat;
            background-position:center;
			margin:auto;
        }