Yo
@CoiL I got ZS10 reaching 100 hours by now. Its maybe the best KZ for me to date, got nice sub bass and mid bass, smoother than previous KZ, following harman target as well.
But compared to KP, KP is more smooth sounding / mature. Sub bass is bigger on KP, but ZS10 punch harder on drum kicks (mid bass section), a little bleed to mid (just a little bit, very far better than previous KP, or **** or BQEYZ) mids a bit recessed compared to KP, clarity cant match KP, treble on ZS10 is brighter than KP.
soundstage quite good, not as large as KP but better than most budget iems, sound separation is very good with micro details, the multi BA setting has the advantage here, similar if not a little bit better than KP. For $35 they're good enough, Depends on your friends budget. If he can stretch up until $100, i would recommend to gamble on tfz no 3 since BGGAR loved his KP so much but he prefer no 3 in recent video.
*edit : i just bought TFZ no 3 not long after wrote this