Creating multiple columns without changing the markup would be very difficult.
Luckily for you though, you can take advantage of CSS multi column layouts here(developer.mozilla.org/en-US/docs/Web/CSS/CSS_Columns/Using_multi-column_layouts)
Doing something like this should work for you:
article {
-webkit-column-count: 2;
-moz-column-count: 2;
column-count: 2;
}
You can take a look here for detailed description on all the column properties: css-tricks.com/guide-responsive-friendly-css-columns/