The comparison between Zac and Light Yagami (aka Raito Yagami and Kira) predates the announcement of the movie because they just look so similar. But now more than ever it is important that the people who matter (like the producers) realize how perfect Z is for this. Seriously, done well, Death Note would be an awesome live action film and it would really be a departure for Zac since not only is Kira a very complicated character but also Z's never done an action film and this isn't a story for the kiddies.
Since really the casting for Kira is a no-brainer the next question is who should direct?
Here are some comparisons for those who are interested:
There are more here.
And there is lj community about it: zefronforkira
Oh, if you want to know "What is Death Note?" click here.