I finally managed to get three prominent WPs to agree on how to handle this particular problem. The consensus view is to ignore the word completely in English. Even in German, it's not used much nowadays, as apparently it has its roots in theory going back 50 years or so.

The IDW Standard Ted refers to says that the UW (EV) can be computed either using the Ertragswertverfahren (income capitalisation approach), i.e. a P&L-based approach, or using the DCF method, i.e. a cash flow-based approach. Either way, what you arrive at is the UW as a ZEW.

In English, we just stop at the UW/EV, as we evidently just don't have the concept of a ZEW. So in your sentence, the most sensible thing would be to leave out ZEW altogether. It doesn't change the sense of the source text at all, even though at first sight it looks like the sort of cop-out we all criticise in other people's translations :-)

Somethings, I think, we just have to know when we're beat.