<el-tree :props="props1" :load="loadNode1" lazy="" show-checkbox>
var Main = {

data() {
  return {
    props1: {
      label: 'name',
      children: 'zones',
      isLeaf: 'leaf'
    },
  };
},
methods: {
  loadNode1(node, resolve) {
    if (node.level === 0) {
      return resolve([{ name: 'region' }]);
    }
    if (node.level > 2) return resolve([]);
            
    setTimeout(() => {
      const data = [{
        name: 'leaf',
        leaf: true
      }, {
        name: 'zone'
      }];

      resolve(data);
    }, 500);
  }
}

};
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')