you can but its not a good idea
treatment of texts is usually 55-45 or 60-40
66-33 is kinda pushing it
a better idea would to be either like blit said Text A + Text B for one idea and Text A + Text B for second idea, so 4 paragraphs
if you can't write that fast a slightly more difficult but easier to get way with less words is using three ideas and having each paragraph idea based and using both texts in each one
it takes more sophistication and you have to make sure you draw everything together tightly
but it generally is more impressive than a similar 4 paragraph one because of the synthesis and conceptual nature
If you're aiming to keep a 50:50 balance between your prescribed and related, it would mean that your related paragraph would be pretty lengthy. The only reason why it might not be good is that the marker might get lost in the paragraph, unless well written. Which is why, most people stick to prescribed, related, prescribed, related.