Not a good idea, in general it would be nicer to use the shared copy of zlib already present in the system, to avoid having to load more data (zlib is almost always already present in memory) and to allow fixes in zlib to be shared by its users too.
Created attachment 119709 [details, diff]
Use external zlib in Compress-Raw-Zlib
Attached a patch to use system zlib.
Created attachment 120134 [details, diff]
Thanks to Ismail, I've been able to test the attached patch for the ebuild (Ismail's patch is bigger than the actual file to replace, and as only those variables are present and documented, this should do it).
bumped with a variation of the second patch (except invoking multilib so lib64 would be correctly captured, or lib128, or lib1024....hey, some day...) Thanks!