Is not posible embed an iframed resource into blog, forum post etc.  It does however work for text and media areas, descriptions for Books and chapter contents, pages, assignments.    This is due to TinyMCE stripping out the HTML required in these areas. 

When you put the embed code, this code not working.

 This is the view after save the changes;https://i.imgur.com/YnlhzNX.png 

And this is te result: https://i.imgur.com/wri4Bk8.png 

Note this may be intentional behaviour. this needs to be reviewed internally by HQ