I would not classify the AS10 as an upgrade to the ZS5v1, but as a great sidekick. They are both excellent for their price, and different from each other enough to justify having both around. They are currently my favourite IEM.
The AS10 has a faster bass and a more coherent behaviour with all kinds of music. The treble is more refined and laid-back (but not sleep-inducing! It is still energetic and clean, while not suffering from the typical new-gen KZ sibilance). In terms of spacial definition, the ZS5v1 is slightly better, with a wider and deeper soundstage and imaging, while the AS10 puts the image somewhat too close to your head and you need more brain processing to get things more defined.
Regarding comfort, the AS10 is smaller and the housing is rounder. My big ears and ear canals don't get affected with either one of them, but for those with smaller ears, the AS10 seems to hit a soft-spot. If you feel the ZS5 pressing against some part of your ears with its sharp edges, you won't have a problem with AS10.
What I don't like about them: the original cables. The ZS5 comes with that greenish piece of crap. Both come with that memory wire. All my memory wires were removed from the cables, and in the AS10's cable, the removal stripped of one of the wires from the plug, ruining the cable. Currently, one of my ZS5 is with a KZ USB-C dac cable, the other is wired with a KZ silver(?) and copper grey (brownish) cable, and the AS10 with a TRN 8 conductors black and silver cable.