Sorry if this has been covered before, but zed is too short a parameter. Origins?
My WAG is that since “zed” is the word for “z” in French, and much of Canada is French speaking, it just crossed over.
“Z” is also “zed” in England, which makes up the rest of the Canadian language
Pronunciation of Z depends entirely on what you were taught at school. Here in New Zealand we pronounce it Zee but lol on talking to my husband as I write this he was brought up with Zed and says that Zee comes from Sesame Street??? 
Zed Zed Zed
We were brought up on zed. Everyone says zed. Where I am being a former British Colony, I guess it’s a colonial hangover. Now, with American television channels, enough people say zee for it to be recognizable as a zed-substitute. So much so that we actually have a TV channel called Zee
I guess zed is Brit while zee is American - or is it much more complicated than that?
It is just a matter of tradition I think and extends to more than just the letter Z - for example why do we call A ‘Aiy’ and not ‘Ah’ (like the French do)?
The word ‘Zebra’ is pronounced differently by Brits (the ‘e’ is a short one as in ‘bed’) and Americans (‘Zeebra’) - I suspect though that this must be effect rather than cause.
In Ireland A is often pronounced “Ah”.
My Malyasian mum uses ‘zed’. She picked it up from the Malay (ie, Commonwealth) english system.
You mean when reciting the names of the alphabet characters?
In England it is “Aiy, Bee, See, Dee, Ee, Eff, Jee… Eks, Wy, Zed”
In France it is “Ah, Bé, Sé…”
Is that what you’re talking about?
Well, I don’t know about reciting the names of the characters, but when spelling out a word, yes. And it’s not the only unusual (to my American/ your English ears) pronunciation here. My username, for example, might be spelled out:
Or, You, Ah, Dee, Haitch
as opposed to the Ar, You, Ay, Dee, Aitch way that you and I would say it.
That first sentence made no sense, did it? I should have said:
“I don’t know about reciting the alphabet, but when spelling out a word aloud” …
Of course, to British ears/eyes, the thread title seems ridiculous. You read it to yourself as “Why do Canadians call a zed zed?”. To which the only answer can be, “Duh!” 
As far as I know, the US is unique among Anglophone countries in having the “zee” pronunciation, although of course the export of (aagh) Sesame Street worldwide is probably influencing the tongues of formerly zed-loving kids…
I was interested to hear that “zee” is common in New Zeeland these days, though…
When I was learning the alphabet, it was A (rhymes with baa)and Z (Zed)
But about the same time, we got children’s TV and Sesame Street so we heard the Alphabet song:
ABCDEFG HIJKLMNOP QRU TUV W X Y and Zee. Now you know the ABC, you can sing along with me.
And that sounded really weird because they mispronounced Z.
I think that this song, and Sesame Street in particular, is responsible for the mispronounciation of the letter Z. Although you could also accuse the letter V because of the rhyming scheme.
Around the same time. I remember my English Cousins learning the alphabet phonetically: Ah ba ka da eh feh geh etc. I hope that that has died a death.
Whatever happened to that bearded rock trio Zed Zed Top?
Actually, I’ve grown to start using “zed” after too much time in phone support. Trying issuing customers from all over the country (that come from all over the world) a serial number with a “z” in it and you usually get this:
Me: “1-2-3-4-zee”
Them: “Vee?”
Me: “No, zee.”
Them: “Vee or zee?”
Me: “Zed.”
[Pulp Fiction]
-
Who’s Zed?
-
Zed’s dead, baby. Zed’s dead.
[/Pulp Fiction]
The “zee” pronounciation obviously for rhyme value. Rhymes with “bee,” “cee,” “dee,” “ee,” “gee,” “pee,” “tee,” and “vee.”
No letter rhymes with “zed.”
Why isn’t the second letter of the alphabet called “bed”, then?
Because the names are not logically derived, they are simply names - you might just as well be asking why the second letter isn’t called Buhbeeeeeewooo!