Hi JThibault,
You can read some of my thoughts about Enso (one of many Zinus brands) in post #2 here and a forum search on Enso (you can just click this) will bring up more feedback as well.
I would never buy any mattress where they don’t provide the density of the foams they use (so you can make sure there are no obvious weak links and can make meaningful comparisons with other mattresses) and they tend to use lower density memory foam than I would be comfortable with (see the memory foam guidelines here) although they are CertiPur certified. “Pieces” of memory foam would also be less durable than a solid layer of memory foam.
Phoenix