Easy answer: Nabu wins ....everytime.
Why?
Well, in Day of Vengeance issue# 1, Nabu says:
'Spectre killed Shazam ....one of the Lords of Order.'
Hence Shazam, the Wizard, is one of the Lord of Order (later explained to be one of the powerful ones from the 9th age of magic).
Then the Spectre goes ahead and kills all the other Lords of Order (and Chaos as well), until only one is left.
Nabu.
Later on the Spectre says: 'I've destroyed all of the lords of order and chaos, save you. You're the last surviving guardian of the 9th age of magic.'
To which Nabu replies: ' And the most powerful.'
Later on the following conversation occurs:
Spectre: "I wasn't powerful enough to destroy you the last time we met, but now I am."
Nabu: " You're deluded as always, Spectre. The last time we met you weren't fighting me. You fought Doctor Fate. I'm not Fate. I'm Nabu, the last and MOST POWERFUL LORD OF THIS AGE."
Conclusion: The Wizard Shazam is powerful, and he does dwell (or used to) in the Rock of Eternity.
HOWEVER Nabu is stronger.
i was about to ask who won between spectre and nabu then i realized well if that happend in issue one and spectre lost there wouldnt have been an issue two : /
Actually the way DOV is written is kind of funny.
In the Countdown to Infinite Crisis that is where Spectre kills Shazam.
This month however Infinite Crisis DOV 1 (dated March 2006) came out, whereby Spectre finishes killing the remaining Lords of Order and Chaos (apart from Nabu).
That is where Nabu faces off against Spectre, and without spoling it for those who havent read it (and want to) let's say certain things change.
Yes... but remember Shazam took Spectre down even he was not full power (damn Mordru!!). Shazam full power cld be pretty impressive and full of surprises. Nabu is powerful but a little high abt himself.
When Shazam gives the power to the resepective heroes .... does he have to ask the God b4 hand i.e. Zeus is part of the quintessence and yet he is powering one of Shazams spells ?
Whose more powerful Shazam .... or the wizard who created the philosophers stone and Etrigan ?