Qualcheduno
100+ Head-Fier
+1If you didn't like the ZST, you certainly won't like the ZS5 because it sounds almost identical.
What specifically didn't you like about the ZST? Too much bass? Sibilant? Too bright? Fitment/comfort? Not fast enough response for metal guitar? Vocals didn't sound good enough?
Also, Aproear is a reliable place to check. Vidal is an active HF member, and his reviews are short, sweet, clear, reliable, and honest. He buys all of his IEMs himself, so no shady biased reviews like some other sites.
He currently has over 140 of ChiFi IEM reviews, and the information is searchable and sortable. Most of his reviews mention musical genres, and I've seen a number that are recommended for rock and metal. So give his site a try as well.
http://www.aproear.co.uk/
Vidal's site has been a valuable source (among other sites) when searching for my first chi-fi iem, just keep in mind that he seems to have a soft spot for clarity and treble oriented iems, so you have to take that in account when looking at the scores.