That is because we were taught the alphabet by the Romans who in turn were taught it by the Greeks, and then we had those people from Scandinavia come across and mess up the whole of our teachings and we got Geordies, who are the decendants of wayward Scots who escaped over the border... And on the other side of the country we had the Irish educating (trying to) the Liverpudlians and Mancunians and when they came south they met the Yam Yams from the Black Country and they all clubbed together and came south to meet the Cockneys... And so once they all understood each other, they decided to expand and sent some West where they missed Ireland and Iceland and bumped ashore where they met another race that they had to educate again... But not only that they sent some South, the idea was to teach the Onions (French) the language of the day, but they missed that bit of land altogether and just kept going untill they bumped into a land where the natives had short arms and jumped up and down a lot.... But getting back to the letter Z - Zee is the sound the arrows made as they passed by you in the battle of 1066 and Zed is the sound the arrow made when it hit you, so Zed became the adopted sound of the end of the alphabet as in Zed Dead.....