Add explicit braces to avoid dangling else
if (lSeek!=0) if (ZSEEK(s->z_filefunc, s->filestream,lSeek,ZLIB_FILEFUNC_SEEK_CUR)==0) lSeek=0; else err=UNZ_ERRNO;
↓
if (lSeek!=0){ if (ZSEEK(s->z_filefunc, s->filestream,lSeek,ZLIB_FILEFUNC_SEEK_CUR)==0) lSeek=0; else err=UNZ_ERRNO; }