In the end I received the hybrid version !
I really like them, a lot actually. They have a similar tone to the ex450 with less bass, but a soundstage a bit bigger and especially more détails.
At first, when I received the Zst, I enjoyed them a lot, but now, I find them completely different.
Like, it's a bit hard to explain.
If I listen to the ex450, ex650, urbanfun, einsear t2, uiisii hm7, they all share a common feature : The sound is a bit similar.
For instance, if I take the urbanfun as a model, I can say that to a certain extent, the other iems have a similar "base" sound.
For the Zst, it's completely different !
The sound is so much different from my other iems, it sounds muddy and a bit lifeless.
....
What, I've just tried them just after writing this and now I find them "normal", as in, totally not like what I just wrote.
I don't understand, I feel like everytime the way I hear/perceive music changes...