Zenzizenzizenzic

Zenzizenzizenzic is the eighth power of a number. Robert Recorde in "The Whetstone of Witte", published in 1557. Although his spelling had the last letter of the word as k.
This word is not used any more in math except as a curiosity. The Oxford English Dictionary has only one citation for it. It survives because it is unusual.
The root word, is the Italian "censo", meaning squared.
Zenzizenzizenzic is from a time when there was no easy way of writing the powers of numbers except as squares and cubes. The fourth power was represented by the square of a square. Zenzizenzic is a condensed form of the Italian censo di censo, used by Leonardo of Pisa in his famous book "Liber Abaci" of 1202.
The eighth power is by extension zenzizenzizenzic. Similarly the sixth power would be zenzicube, the square of a cube.
Zenzizenzizenzic has more Z's than any other word in English.