As detailed in https://www.playonlinux.com/en/topic-15142-Outdated_POL_zlib_libraries_break_32bit_Wine_prefixes.html
Seems to affect all 32bit games, not just LoL.
Sorry for double comment, but an Arch Linux temporary solution has been found by user Fincer:
I can confirm it. All arch based distributions suffer from this! Please fix ASAP.
This happens to me not only on 32 bit, but also on 64-bit prefixes with 64-bit programs in them. I downgraded lib32-libpng to 1.6.27 like mentioned in the thread above, but also had to downgrade libpng to 1.6.27 to make 64-bit programs work again. Thank you for sharing the quick workaround, hope this gets fixed. Trying to fix this issue leads to some websites talking about removing the freetype libraries, which is really not what you want to do.
From what I understand, we need to rebuild every wine version right?
At least the solution I've suggested works without re-compilation of Wine versions shipped by POL. I don't know how much you rely on these outdated library files so I guess the answer to your question is
1) either you should re-pack all Wine versions without zlib (possible?)
2) or re-pack all Wine versions with newer zlib files (which are supported by libpng version 1.9.29 and above)
You may also consider contacting libpng developers, explaining the situation & pinpointing the commit which broke the compatibility with the old Zlib libraries.
Isn't libpng also bundled in the package?
Same problem exists on fedora 26 too. I believe the problem is with freetype2 (or lib32-freetype2) which depends on newer versions of zlib (or lib32-zlib) and libpng (or lib32-libpng). Since there isn't any specific version of libfreetype.so included when you download a wine version (when you are not using the system's wine), then the zlib libraries shouldn't be included too.