The zsh completion script (/usr/share/zsh/functions/Completion/openSUSE/_zypper) does not handle global options prior to the command. For example if you type

% zypper search

and then hit <tab> it gives you the valid options for the search command. If on the other hand if you type (the perfectly valid):

% zypper --no-refresh search

and hit tab, it doesn't give any valid options even though it should give the same options as in the first example.

If you type:

% zypper

and hit tab, it correctly lists the available global options along with the commands but if you enter one of the global options it will not do any further completion.