Hold on a second…
Last check, “zeds” in American English was a slang term for zombies in mobile-based (Java era, pre-smartphone) zombie shooters. Taking a nap in American English was “catching Z’s”.
While in European English, “zed” was the pronunciation of the letter Z.
When did THIS changeover take place? First I noticed was when the US seemed to adopt the Euro pronunciation of “aunt”, and I only found that out a few years ago.
(Yes, I’m a geek. And a linguistician. And I’m writing a new dictionary.)
John Zakour and Scott Roberts