Feature request: support zref and zref-clever

[qcts33]

First of all, thanks for this excellent work!
It would be nice to support the zref and zref-clever package as an alternative reference system.
The zref package provides the extensible referencing system with the \zlabel command. The zref-clever package is based on zref and provides the same functions as the old cleveref package, but using the \zcref command.