@-moz-document url("chrome://browser/content/browser.xul") {

#zoombar-toolbar[cui-areatype="toolbar"] toolbarbutton#zoombar-toolbar-increase {
list-style-image: url("moz-icon://stock/zoom-in?size=menu") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
}

#zoombar-toolbar[cui-areatype="toolbar"] toolbarbutton#zoombar-toolbar-decrease {
list-style-image: url("moz-icon://stock/zoom-out?size=menu") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
} 

#zoombar-toolbar[cui-areatype="toolbar"] toolbarbutton#zoombar-toolbar-reset {
list-style-image: url("moz-icon://stock/zoom-original?size=menu") !important;
-moz-image-region: rect(0px, 16px, 16px, 0px) !important;
-moz-box-orient: horizontal !important;
} 

}