The zeely zero is named for Zeeland Michigan.
Party animals in Zeeland are the odd ones out, so they usually go to Holland for a good time.
That might seem strange to somebody who doesn't know Zeeland. Any activity in Zeeland is most likely going to be low key, lights out, and face down.
Sexually, the population seems to be mostly traditional and male-superior. That means that most of the men who stay at home and indulge their fantasies usually do so doggy style.
So women in Zeeland who like their men that way are said to prefer the Zeely Zero. Zero means no face to face contact during sex. Therefore, mostly zero interaction satisfaction. They might know what it feels like feel but they might know nothing about the person who it belongs to. Zero again.
Overall, then, the zeely zero is not a good thing.
He told her that her looks weren't important. She thought that was a good thing until she found out it meant she would always be face down on the floor during sex.
Damn, she said, I hate zeely zeroes. I'm heading to Holland for a dutch treat.