I recently got the Somics, also I have the zst, zs3 and a few others KZs(ATE and ED9) for a few months now. My favorite KZs are the ZST and the ZS3 (in that order).
Now that I've been using the Somics V4 for a few days, and after some burn in, I have to say the in fact they're overall (SQ only) superior than the ZST, but actually not by that much,oh and a big little thing (for me), the bass in the Somic v4 is a little bit recessed for my tastes, I already tried a few eartips to get a better seal, wich helped with the lower frequencies, but they still lack some bass (again, for my tastes), this can be solved with a little EQ, but the thing is that the signatures of the zst and zs3 didn't need any EQ to be pleasant for me.
Thank you! Yes, I heard that the Somic V4s are not for bassheads. I am not a basshead, but I do like deep, punchy bass as I listen to a lot of chillout trance, liquid dnb, etc. I hope the EQ would help a little. Bass is one thing that I like with my ZST, ZS3 & especially with the MEMT X5. I guess it is difficult to find a budget IEM around $25 that ticks all the right boxes as far as my preferred sound signature is concerned.