Recently got my hands on KZ ZS5 (present from girlfriend) and I must say it's WAY better than the ZS3. I mean there is NO comparison between these two. here are my initial impressions after about 6 hours of cumulative experience:
Comfort: Only thing that the ZS3 does better is the shape of the housing and therefore higher comfort levels. Not to say the ZS5 is uncomfortable, especially with other tips like sony hybrids (which don't really change the sound much) or any other softer, less rigid flange tips. I have some no name foam tips coming from Aliexpress, and will say how those perform. Right now though I have a VERY wide bore and almost as soft as the Sony hybrids tips and well, they are pretty comfortable. Don't know what they are or if you can get them, AFAIK they came with some earphones bundled with my General Mobile GM5 so yeah... As for the included star tips are too rigid for my preferences and Sony hybrids sound no different so go for Sonys. The memory wire portion (you know, the actual metal wire underneath the sheath) was absent on the ZS3 and it was horrible until I completely cut the thick rubbery memory wire sheath off. The ZS5 does have the proper memory wire and when fitted correctly, they do not hinder me in any way... all in all, they might not be as comfortable as the "memory wire removed" ZS3s with small sony hybrids, but with larger Sony hybrids (these do sit in years differently, therefore the larger tips) and properly formed memory wire, they are pretty good for longer sessions.
Build Quality: They are built well. no apparent flaws. all the wents are open and there is no drier rattle and loose connections with the wire etc. larger "seam" is a design aspect, rather than finishing defect, so yeah - no qualms. these are not fragile or weak and I'm pretty sure with normal use, they will hold up (Gym is not a normal sue scenario, sweat will find ways into the vents and *** everything up).
Sound: I own several phones, most notable are the KZ ZS3, Sony XB90EX, Seenheiser HD598, hisound BA100. This is my Second KZ and first Hybrid of any sort. It is also the BEST Sounding one out of those that I own. These are the Fastest sounding of them all, meaning that they are VERY detailed and can handle busier music passages without distorting, hiding certain frequencies or instruments and without making the music sound like a big much of noises. even with unforgiving music like Maximum the hormones shimi, or the Tools parabola, everything is present and every little detail is still in the mix. the zs3 for example can't really do that, nor the HD598 can handle those. tips don't really change the sound as much (I didnt really notice any, except for a little more treble with the aforementioned super wide bore tips. a
ZS5 also makes it easy to distinguish the perceived direction from where the certain sounds come from. it's as good as the XB90EX with that. not The "soundstage" is also almost as big, but some sounds can be more upclose with the ZS5 and some are even further, when compared to the XB90EX.
ZS5 has a pretty good sound signature. I'd say they emphasize treble and sub-base, but not overly so. some recordings with poor mastering don't sound as good as others but overall it's not the ZS5s fault imo. base frequencies are pretty controlled and they do not bleed. crappy hip/hop recordings with artificial rumble sound artificially rumbly, while good mastering examples (tech n9ne for example) really shine with energy and control. Mids are there and can be VERY luscious and sweet (miles davis blue in green sounds almost as sweet and lush as on the XB90EX), but can be small and thin at times (again, this is entirely up to the recording). treble is there and it is pretty detailed and sparkly but never grainy or over-stressed and sibilant. I guess this is the biggest plus of the multi driver phones - they can handle stuff easier and with less effort. The whole listening experience is just like that - effortless and doesn't feel busy or crowded. This imo is the biggest pro the ZS5 has.
These are pretty sensitive to source though. they make the crappy sources sound pretty bad (my phone for example, which I'm pretty sure uses the same DAC that early 8 bit video game consoles used back in the day) and good sources
Mind you I've listened to these from the Ibasso DX50 on the latest firmware, my Desctop pc sound card (ok sound from these) and my phone (UGH). I'm pretty sure some placebo effect might be at play here but I've tried to not fall for it and I'm also pretty sure these are a steal at 30-ish, moreso at the 18$ deal. anyone who doesn;t have a highend earphone and wants to hear something good, get these.