Screenshot shows the original on the bottom, compact one up top, with (what else!) full accumulators to show the output.
There may not be a lot of call for a Factorio-style 4x4 balancer in DSP, but when you need one, you're gonna need one. This one's a little wider than the original, but a bit shorter, too. You can chop the input and output belts short, too, for even more space savings. If you're really needing something crazy, you can even lop off one of the two input splitters and chain the result directly onto the end of one side of this in order to expand it out to more belts.