text: Q:
  
  Changing z-index for google map data layer point
  
  I have created a google map with circles overlapping each other, while am hovering overlapping circle, z-index of that circle should changes and it should come on top of other circles. There is a way to do this for markers, like in this link "
  changing z index of marker on hover to make it visible " . But i want to do this for points created by data layer, Here is my fiddle sample 
  http://jsfiddle.net/8cs97z8h/1/
          var json = {
              "type": "FeatureCollection",
              "features": [
  
                  {
                      "type": "Feature",
                      "geometry": {
                          "type": "Point",
                          "coordinates": [-98.344139,28.629211]
                      }
                  },
                  {
                      "type": "Feature",
                      "geometry": {
                          "type": "Point",
                          "coordinates": [-98.341263,28.629228]
                      }
                  }, {
                      "type": "Feature",
                      "geometry": {
                          "type": "Point",
                          "coordinates": [-98.3412, 28.629]
                      }
                  },
              ]
          };
  
          var map = new google.maps.Map(document.getElementById('map-canvas'),      {
                  zoom: 12,
                  center: new google.maps.LatLng(28.666767, -98.367298),
  
          });
          map.data.addGeoJson(json);
          map.data.setStyle(styleFeature);
  
     function styleFeature(feature) {
              return {
                  icon: {
                      path: google.maps.SymbolPath.CIRCLE,
                      strokeWeight: 2,
                      strokeColor: 'white',
                      fillColor: 'blue',
                      fillOpacity: 1.0,
                      scale: 7
                  }
              };
          }
  
  A:
  
  You may use overrideStyle to achieve it.
  Set a variable where you store the zIndex and apply this zIndex in the setStyle.
      var zIndex=1;
      //Setting style for markers circles.
      function styleFeature(feature) {
         return {
              icon: {
                  path: google.maps.SymbolPath.CIRCLE,
                  strokeWeight: 2,
                  strokeColor: 'white',
                  fillColor: 'blue',
                  fillOpacity: 1.0,
                  scale: 7
              },
               zIndex:zIndex
          };
      }
  
  Then add a mouseover-listener where you increment the zIndex and apply it to the feature:
  map.data.addListener('mouseover', function(event) {
         map.data.overrideStyle(event.feature, {zIndex: ++zIndex});
  });
  
  Demo: http://jsfiddle.net/8cs97z8h/6/
  
  