A Male and a Female were sitting on a bench in a garden. The Gardener asked the Male, "What is your relation with this Female?" the Male replied, "Her mother-in-law is the daughter of my mother-in-law."
What is the relation between them?
The female was
the daughter in law of the male.
"Her mother-in-law is the daughter of my mother-in-law" can be simplified to
"Her mother-in-law is my wife"
which implies that the female is his wife's daughter in law and also his daughter in law.
Another possible answer:
The phrase "the daughter of my mother-in-law" can mean wife, yes, but it could also be his sister-in-law, if he is married to one of her brothers. So then the female on the bench would be the daughter-in-law of his sister-in-law, making her his niece-in-law-in-law (and if you know enough genealogy to come up with a better name than that minor disaster, please don't hesitate to post!)
The obvious answer...
An alternative answer...
The male would call this female his niece(-in-law). The female's mother-in-law's mother could also have another child to whom the male is married. The female's mother-in-law's child would be his spouse's niece/nephew, and hence his own niece/nephew. Technically, this person's spouse would be his niece-in-law, but colloquially, he would probably call her his niece.