Supergirl has more romantic troubles, and Zatanna's back up series comes to an end in Supergirl 4 (March 1973).
Bates, Saaf and Colletta open the Supergirl story with Linda Danvers at a pool party, where a new student, David, has quickly become her new beau. She doesn't know very much about him. For example, she has no idea that he uses his university student life as a cover while he leads a criminal gang. The reader learns this when he meets with underlings when an earthquake disrupts the party. Since Linda takes off as Supergirl to stop the quake, she doesn't suspect a thing.
Later, David tries to prove what a good guy he is by diving into the damaged pool to stop one of Linda's roommates from injuring herself. He winds up banging his head on the broken pool bottom, and winds up in a coma.
As he is in danger of remaining in a vegetative state forever, Supergirl contacts the Kandorians and gets a brain cell extractor. She uses it on herself, and then implants her brain cells in David.
This not only cures him, it also gives him temporary super powers. He uses them for crime, and only then does Supergirl find out her boyfriend is a thief. The powers wear off, and she brings him in, once again to be dateless and alone. Aww.
Bates and Heck end off Zatanna's brief run with a story that sees her get trapped in a stone. She is in a park when weird, magical things start happening.
The source of the problem is a rival magician, a descendant of Merlin. He tricks Zatanna into getting trapped in a stone, like the sword from Arthurian legend. Her magic is not strong enough to free her, as this was one of the original Merlin's spells.
Zatanna sends her astral form to retrieve the only living descendant of King Arthur, to pull her out of the stone. This proves to be an infant. He must have been adopted, because we see the boy with parents, and one would expect that either the father or mother must also have been a living descendant of Arthur.
None of Zatanna's stories in this run have been really stand out. The first was the best.
The following issue does have a Zatanna story, but it's a reprint of her first appearance, from Hawkman 4. Zatanna is next seen, a few months down the road, in Superman's Girlfriend, Lois Lane.