I can open up the new Eusebius Ecclesiastical History English + Greek texts one on top of the other in the iPhone app and get them to sync and scroll together.
But when I tried to open up both books side-by-side on my computer (PC) and then linked them so they could scroll together, whenever I scroll one the other changes to the same resource. I.e., I'll start with English on the left and Greek on the right, but when I try to scroll, e.g., to the Table of Contents and then scroll from there, I find that I now have two English editions side-by-side; the Greek has changed to the English volume.
Weird (unless I'm doing something wrong).
http://www.logos.com/product/30595/the-ecclesiastical-history