Zenzizenzizenzic represents the square of the square of a squared number. It is the eight power of a number.

((n²)²)²

This term has its root in Italian censo which represents square.

Latin: census→ Italian: censo (square) → German: zenzic (squared) → English: Zenzizenzic (square of squared number) → English: Zenzizenzizenzic (eight power)

Robert Recorde in his seminal work, The Whetstone of Witte, published in 1557, used the term zenzizenzic to represent the fourth power of a number. Zenzizenzizenzic is an obvious derivation of this term.  Medieval English had limited terms to denote the powers of numbers. Apart from square and cube, the other powers had to be expressed in formulae or written in plain words.

Recorde also used the term zenzicube to represent the sixth power of a number which is the square of its cube.

(n³)²

Though obsolete, these words attract a great deal of historical curiosity. Zenzizenzizenzic has more Z's than any other known word in English language, 6.

Facts and Figures: http://thefactbox.blogspot.com