Implemented code in the Android WebViewRenderer

WebViewRenderer.cs

void UpdateEnableZoomControls()
{
  // BuiltInZoomControls supported as of API level 3
  if (Control != null && ((int)Build.VERSION.SdkInt >= 3))
  {
    var value = Element.OnThisPlatform().EnableZoomControls();
    Control.Settings.SetSupportZoom(value);
    Control.Settings.BuiltInZoomControls = value;
  }
}
void UpdateDisplayZoomControls()
{
  // DisplayZoomControls supported as of API level 11
  if (Control != null && ((int)Build.VERSION.SdkInt >= 11))
  {
    var value = Element.OnThisPlatform().DisplayZoomControls();
    Control.Settings.DisplayZoomControls = value;
  }
}