ZRAM compresses memory on processes not being used for a certain time (that are on the background). When they are brought back to the foreground, it decompresses at a little cost on the CPU for a moment. That is great for machines that do not have much memory because it prioritizes what is being run regarding RAM - and that is also great to eliminate completely the need to use swap on disk when a machine has plenty of memory. But if an app uses many processes it may cause the opposite effect (some slowness). PopOS claims that is not a problem on their implementation that was enabled some months ago. Fedora also implements ZRAM for some time now.