const observer1 = new ResizeObserver((entries: any, ob: any) => {
      console.log('observer1 zone', Zone.current);
      for (const entry of entries) {
        console.log('observer1 resize entry target', entry.target);
        console.log('observer1 resize entry size', entry.contentRect);
      }
    });

    observer1.observe(div1);
    observer1.observe(div2);
    Zone.root.run(() => {
      observer1.observe(div3);
    });