Please check the demos I have posted before. You are not using any of the recommendations. 

The 1st block could be done by using show only a part of the iframe and the other one hiden with the hide part of the iframe. And for both you should use media queries. Of you hide both with hide part of the iframe with media queries. As one block is in the middle you would have while spaces. so you might replace (= overwrite) it with your own banners. 

Best regards,

Michael