Good advice LT. I don't think there is anything wrong with saying "tell ya what, why don't we discuss this more when you're a little older". I think that an adult religious debate is too much for a young kid to handle emotionally, especially when mom and dad clearly have different ideas. Though I know that it would be tough to avoid getting really deep into topics like this with Zach, because he's such a smart and curious kid.
Hehehe, Dan's had first hand "dealings" with Zach. As soon as he walks through the door when he visits...Zach has computer "programming" to "teach". So yes, he's full of questions especially when he hears us talking the deep subjects. The "we'll discuss this when your a little older" just sometimes don't fly with him. But, there's a lot of good advice here. Lots to think about.