Comment # 8 on bug 1175967 from Dirk S.

I've upgraded rpm to the latestest version with --nodeps.
This has broken zypper because my zypper version depended on librpm.so.8
instead of 9.
I was forced to use rpm to update zypper. After some work caused by the
dependencies I am finally able to update again.
I don't know if I should request to close the case because the cause of the
problem is still unknown. Maybe you should provide an updated rpm with zstd
compression included but depending on librpm.so.8 as additional package.
I've got a snapshot of Tumbleweed-20190512 on an other partition as emergency
system. I am not sure if it is possible to update this system easy otherwise.