Are you sure you're not thinking of "naught"? I'll admit I don't know that Brits don't use "Zed" for zero, but I've never heard it from any British YouTuber I've watched, including maths YouTubers, nor any British TV I've watched. But it's possible one of their dialects uses it maybe?

All the ones I've heard say naught though.

For completeness I'll say Canadians typically don't say naught unless they're British themselves, we say zero.