There is a fairly common figure of speech where one deliberately imposes a parallel structure that is not quite grammatical. For instance, consider the question "Is A less, equal, or greater than B?" This is ungrammatical, because while the correct preposition for less and greater is indeed "than", the correct preposition for "equal" is "to". In fact one never says that "A is equal than B." And yet, using this parallel structure is terser and arguably more pleasant than asking "Is A less than, equal to, or greater than B?"
I know there is a (probably Greek) term for this rhetorical device, but for the life of me I cannot remember it. The closest I was able to find was "zeugma", but that doesn't quite seem to fit. Does anyone here know?