Comment # 1 on bug 1203089 from Andreas Stieger

$ zypper search -t package -s libz1-32bit
[...]
S | Name        | Type    | Version     | Arch   | Repository
--+-------------+---------+-------------+--------+------------------------
  | libz1-32bit | package | 1.2.11-19.7 | x86_64 | openSUSE-Tumbleweed-Oss

$ zypper in --dry-run steam
[...]
(valid solution, including libz1),

> Solution 1: deinstallation of libz-ng-compat1-32bit-2.0.6-4.2.x86_64

Pick this one. Local problem, bug invalid with current summary.