No final impression yet, and honestly it is due to me having some difficulty finding the right tips with the ZS3. So from looking at my ZS3, it doesn't seem to have a vent hole; therefore when I push them into my ears it feels like I'm pressurizing my ear. I am still unsure if it's the shape of my ear canals or the shape and design of the ZS3 and the length and width of the stem, but it's really weird. And since I don't want to cause any damage, I don't keep them on long enough to even listen through a song and immediately remove them.
Fortunately, just today I've found a small work around after some experimenting. I'm now using a rubber o-ring before I put the tips in so it pushes the tips out slightly further away from the body of the earphone and further from the tip of the stem. This reduced the pressurized feeling I'm getting but not completely. I'll have a good listen tomorrow when I'm at work.
On another note, the ATR is simply amazing and fun to listen to. No other words are really needed, but if I had to choose between the ATR and the 4in1 when I have to walk outside and wear earphones all day long, I'd easily choose the ATR. The 4in1 sure has a better sound quality but the ATR doesn't fall that far behind. And considering the ATR's only have 1 driver each side, not fatiguing, lighter (you hardly feel the weight), and cost $5 or less, it's just wow...
If you compared the more expensive ZST to the ATR, even though from the price stand point the ZST should be the winner; but it's actually the ATR's win. The ATR is clearer, has better details, it isn't muddy, the bass isn't overly emphasized but it is there (a great sub bass does come out with the right tips), the sound stage is decent and it isn't narrow like the ZST, and it has good imaging. If I had to compare what ATR's sound quality reminds me of, or what it's really close to then it would be the Vivo XE800. The difference being that the XE800 is brighter and more on the cooler side, while the ATR is leaning more to the warmer side. It isn't a perfect comparison but it is close, for $5 it really is a bargain. I've already ordered more to give away as gifts and stocking stuffers for Christmas.