quintillion vs zillion

quintillion

noun
  • Any very large number, exceeding normal description. 

num
  • A billion billion: 1 followed by eighteen zeros, 10¹⁸. 

zillion

noun
  • An unspecified large number (of); a gazillion. 

How often have the words quintillion and zillion occurred in a corpus of books? (source: Google Ngram Viewer )