z & zlevel can be set by option

src/chart/chord.js

@@ -1080,6 +1080,8 @@ define(function (require) {
             opt.itemStyle.normal.label.textStyle = this.getTextStyle(
                 opt.itemStyle.normal.label.textStyle
             );
+            this.z = opt.z;
+            this.zlevel = opt.zlevel;
         }
     };
     

src/chart/pie.js

@@ -874,7 +874,8 @@ define(function (require) {
             opt.itemStyle.emphasis.label.textStyle = this.getTextStyle(
                 opt.itemStyle.emphasis.label.textStyle
             );
-
+            this.z = opt.z;
+            this.zlevel = opt.zlevel;
             return opt;
         },
 

src/component/base.js

@@ -55,6 +55,9 @@ define(function (require) {
     Base.prototype = {
         canvasSupported: require('zrender/tool/env').canvasSupported,
         _getZ : function(zWhat) {
+            if (this[zWhat] != null) {
+                return this[zWhat];
+            }
             var opt = this.ecTheme[this.type];
             if (opt && opt[zWhat] != null) {
                 return opt[zWhat];
@@ -88,13 +91,16 @@ define(function (require) {
          */
         reformOption: function (opt) {
             // 默认配置项动态多级合并，依赖加载的组件选项未被merge到ecTheme里，需要从config里取
-            return zrUtil.merge(
+            opt = zrUtil.merge(
                        zrUtil.merge(
                            opt || {},
                            zrUtil.clone(this.ecTheme[this.type] || {})
                        ),
                        zrUtil.clone(ecConfig[this.type] || {})
                    );
+            this.z = opt.z;
+            this.zlevel = opt.zlevel;
+            return opt;
         },
         
         /**