It didn't actually link. But you're close, though. This part, enclosed in brackets
url="http://www.youtube.com/watch?v=Z3DX4tu7DkE"
has to come first. Then it should be FOLLOWED by the words you want to act as the link, such as--
here
--which should then be followed by /URL, in brackets
Let's do that and see if it works....
here