I've put my hands on foam tips and it seems that experimenting tips holds surprises -honestly I would pay someone else to do it in my place and just return the best results.. given the number of options ..
I've decided to return the ZAS , I find them balanced and well behaving across a number of sound factors ( bass!, separation, image) but just a bit short of personality.
So ZAR with their warm dark analogue character and 10 pro X with their subbass fun monster pounding ( and price ) are in the house now.
AST coming later today for comparison
----- The AST ------------------------------------------------
PROs
- overall the most technically competent of all KZ I tried
- timbral accuracy is much better then rest of KZ across all spectrum of frqs and for a large part of instruments ( from guitars to piano to strings to drums to flutes and violins and voices : the sound is more sweetly fletched and parented with original instruments );
- the mids are the less recessed and more nuanced of any other KZ I tried;
- voices ( both females and males ) sound textured detailed and natural, I have to say I really loved voice natural and detailed airy portraits here..
- the micro details are done better( i.e. subtle voice details or drums decay or portraying different simultaneous tones while preserving them );
- the highs are the less harsh of all KZ ( so you can 'pump them' on eq and not find distortions easily like in the other KZ)no hints of sibilance , metallic edge or haze: zero . If anything highs are natural and slightly sweet sounding ( opposed to edgy )
- mids are very smooth ( more then any other KZ ..again....) , also very nicely rich : nuanced detailed and i would add even 'fresh'
- space effects ( L/R , image ) are nicely precise and done with very smooth organic micro transitioning , not overdone or bold ( think 10PRO X
)
- the tones are more solid then any other KZ I tried
- there's more 'going on' in same music compared to all others KZ I tried ( details , and display of music is better)
CONs
- the bass is there..as it should obviously , there' s nice separation texture and decent speed . But is not authoritative and physical ( ZAR ): even when music'd want and call it to be . So impact may be missing and soft depending on your gears and taste , not awe-fun ( as 10 Pro x, or think Sony-Z1R if you dare ) . Also I wouldn't call speed or prat exciting , so not a typical fun/bass kz iem . A flat textured separated bass with hint of sub base : good enough for some , not enough for others .
- the overall tone is warmish/sweet , with a choice for more decay on notes , giving this set a better insight on details and a subtly romantic drive , but rithmically not enormously fun..
-they have less of a 'special character' ( colour?v shape?u shape? you call your favour ) like other KZ sets , so they can sound equally very good but a tad uninspired depending on your mileage ..for same reasons the "cons" could also read as "pros" depending on what use or joy in the music you have
I'd give them 4 stars
factoring in the price it could be easy a 5 for manys: sure they are technically and timbrally proficient and it is fast thing to tell when on ears
----- The ZAR --------------------------------------------------
CONs (vs AST)
-they loose on them in soundstage (widely ) , in detail / timbral accuracy and highs - which are more supressed , less smooth and more metallic albeit not as much as in the other KZ' iem or more distorted when with eq' ; and surprisingly -had to double check number of times..- they sound somewhat thinner then the AST24 , I wouldn't tell it in first tests but AST are richer and more upfront in mids and this fills it up slightly better imo then ZAR organic warm character
PROs (vs AST)
- the bass is a brick, often solid as dark matter , authoritative , hits supported by a deep-but-tight sub bass dry enough ( no 10Pro X here ) , and can be felt instead of heard wich - even though it preserves some of its nuances to come atop the feeling - I much prefer
-the tone is warm/dark 'down to earth' with a more organic drive on bass/mids ( it is more stagey , airy, sweet and marginally more suspended on AST )
-the speed is definitely better and more fun , you loose a tad of tact in articulation( not much / depending on tunes ) but you gain on prat and impact here.
-the background is blacker : the AST play in the upper atmosphere , rade enough no blacks behind though ; the ZAR play nearer to the black space ( just a hint of air when you eq' highs , and dead black behind )
-overall signature is funnier but more relaxing , it is still interesting to hear the music but you feel flow and fun more then on AST where you tend to look on what's happening in stage a bit more ..obviously mileages may vary here so take these words and considerations as personal
I wouldn't ever say the ZAR are superior to the AST , they are not : and it is evident . But.. some *important* sound things are more in line with my favor on them , and eventually I prefer them over AST...and that brick-bass landing down like a no-sweetener black coffee monolith from the sky (when record allows for it of course ).
I'd give them 4 stars
as they need improving in 2 areas on all : stage and highs show; as well I have to already tell my favour as their overall sound profile and flavour is something special and more solidly akin to my taste
True that if they had better stage and highs i'd be willing to pay them more then AST. And if they had better stage/highs and AST timber , i'd pay them much more..but i assume that at that point some dark brick magic wet of them would be lost or sacrified , they are refined but you have to like a darkish presentation here (> coloured ) , AST warm/sweetish tones are also there but not as evident
----- THE ZS10 PRO X -------------------------------------------
The best fun if valuing bang for bux : ZS10 PRO x
It's behind both by a fair margin on technicals , and doesn't even approach by far being hiend or audiophile thing, but..it would be my choice if I had to select only 1 and on budget and looking for fun on the go, they sound abit hipy not particularly linear, nor silent black behind , but that sub presence and mellow mids are entertainingly fun, with decent enough highs : overall more then decent for providing nice company and portable fun ..
super for the price they sell though
My 2c..hope that helps 
I will be living with ZAR and AST swapping them as my 2 portables of choice for some time, then ..I will update 
