Well, from my initial look. You haven’t specified for any divs nor height or width. The answer is within you question… you want specified equal height…
By default any DIV you create they have values of Auto = meaning they will stretch to child content. In your case you have two images of different dimensions. One on the left has 476x375px and on the right 902x719px if you don’t specify parent div width or height, they will automatically resize to fit the content.
If you wish them to stay in same position. You would need to set some constraints to the parent divs.
For example - set your Div Block 13 height 600px ( or whatever you want )
Div block 41 and 41 height to 100% ( meaning they will be always 600px )
Set both image width to 400px.
And you should see the results.
Hopefully this will get you in the right direction.
But since i don’t know about which elements are you talking I assumed it’s the two images.