Eating at Quonk: A tough puzzle

A group of friends: 2 women (Alice and Babs) and 2 men (Zach and Yabu) like to go out on dates to cool restaurants in pairs. There are four combinations they date in (Alice-Zach, Alice-Yabu, Babs-Zach and Babs-Yabu).

The favourite restaurant of one of the men and one of the women is a place called Quonk. However if those two eat together they always try new restaurants as do the other pair if together. Therefore when exactly one and only one of the particular man and woman in question is on a date they eat at Quonk.

When Alice goes out with Zach they go to Quonk.

Which, if any, other pair eat at Quonk?

Answer

The Maze

The maze

In a big hall rows and rows of people sit at computers writing their names with their mice

The maze

At the end of a long tunnel you can see an alien