Just take a look here: xz — ImgBB

Styles are the same on both columns.

In 90% of the cases even the proofing for both columns is set similar(let's say ENGLISH(US) for both, although we technically have english on the left and german on the right).

I have to manually go all the way down selecting one or more paragraphs at a time(depending on how the file is structured) and hide one language(ALT+Z, my personal macro for fast hiding), repeatedly, thousands of times