Daniël Hooymans wrote:

4) user fills in the list and submits his answers.

This part is inclear to me, but it sounds simple enough.

Is it possible to create such a project not by writing a zope product but fully through the zmi

Yes. (Although it may or may not be the best solution to do it fully through the ZMI. But it is possible, and doesn't seem to complex).

and fully using the ZODB (no SQL)?

Absolutely.

And where do i start ? what are the best practices in implementing such a project in Zope?

You need to decide what a "list" is and how you submit "answers" and how these answers should be stored. Then you try to implement one such list, and tackle the problems one at a time.