Zoom level event change icon size...

test.php

<script>
		jQuery(function($){
			
			var image1 = new google.maps.MarkerImage(
			  '<?php bloginfo('template_url'); ?>/images/marker-images/map-marker-12px.png',
			  new google.maps.Size(12,12),
			  new google.maps.Point(0,0),
			  new google.maps.Point(6,6)
			);
			
			var image2 = new google.maps.MarkerImage(
			  '<?php bloginfo('template_url'); ?>/images/marker-images/map-marker-24px.png',
			  new google.maps.Size(24,24),
			  new google.maps.Point(0,0),
			  new google.maps.Point(12,12)
			);
			
			var image3 = new google.maps.MarkerImage(
			  '<?php bloginfo('template_url'); ?>/images/marker-images/map-marker-48px.png',
			  new google.maps.Size(48,48),
			  new google.maps.Point(0,0),
			  new google.maps.Point(24,24)
			);
			
			$('#map_div').gmap3({
				action:'init',
				options: {
					center:[<?php echo $lt;?>,<?php echo $lo;?>],
					zoom: 6,
					scrollwheel: false
				},
				events:{
					zoom_changed: function(map){
						var zoomLevel = map.getZoom();
					  	if (zoomLevel < 6)
					    	UseMarkerIcon(image1);
					  	else if (zoomLevel >= 6 && zoomLevel <=8)
					    	UseMarkerIcon(image2);
					  	else
					    	UseMarkerIcon(image3);
					}
				}  
			},
			{
				action: 'addMarkers',
				markers: [ <?php echo $lat_long;?> ],
				marker: {
					options: {
						draggable: false,
						icon: image1             
					},
					events:{
					mouseover: function(marker, event, data){
						var map = $(this).gmap3('get'),
					    	infowindow = $(this).gmap3({ action:'get', name:'infowindow' });
					  	if (infowindow) {
					    	infowindow.open(map, marker);
					    	infowindow.setContent(data);
					  	} else {
					    	$(this).gmap3({action:'addinfowindow', anchor:marker, options:{content: data}});
					  	}
					},
					mouseout: function(){
						var infowindow = $(this).gmap3({ action:'get', name:'infowindow' });
						if (infowindow){
					    	infowindow.close();
				  		}
					}
				}
			
			}
			});
		});
	</script>