Based on the search results, here's a breakdown of zswap vs zram:
Zswap is a compressed cache that works alongside a traditional swap device (on disk/SSD). When RAM fills up, pages are compressed in memory first, and when the compressed pool fills, the least recently used pages are written to disk swap.[1][5]
Zram creates a compressed RAM disk that acts as swap entirely in memory, with no disk swap required by default (though it can be configured with a backing device).[1][5]