I would say if it's Irish traditional you're accompanying GDAD is the one. I used to use GDAE but since retuning have never looked back as love to accompany Irish music. Works quite well with Scottish and some of the less morris-like English tunes you might play too. There are good players from all of our Island traditions and it seems to fit into our music style perfectly.

That said, the zook is an instrument that is begging to be experimented with due to it's relative infancy so I would say whatever takes your fancy.

Enjoy your zook Don!

stigWeard