you are not even close lol. a $200 iem upgrade will probably be night and day from the kz zs10 pro, maybe even with the $80 hexa, or a $20 waner, let alone an end game iem or headphone.

for example, crinacle rates the zs10 pro as a C tier iem, whilst rating the Moondrop Chu as a B tier iem and the Letshuoer S12 as a B+. the difference between the Chu and S12 makes the Chu sound low fidelity, granted however, i believe the chu is overrated and should probably be closer to C+ in the current market. The Variations is another iem i have spent quite some time with, and with crinacle rating it an A+, it is again night and day compared to the s12 in sound quality. the disparity between the chu - s12 - variations is pretty sizeable imo, with each sounding leagues better than the other, ie chu is 4/10, s12 is 7/10 and variations is 9/10, and i know you cant really quantify audio but variations certainly sounds more than twice as good as chu. so, with you on the zs10 pro, an end game level iem or headphone will definitely be quite the sizeable upgrade, probably the same level if difference between a $2 supermarket earbud and ur zs10 pros in the first place. i think diminishing returns only truly begin after like the variations, where id be surprised if you can squeeze much of a difference, though i havent tried anything more pricey than it.

if i were you, id really recommend getting a budget fi option like the tangzu waner, it is probably a sizeable upgrade from the zs10 pro, if crins ratings are to be referenced.