co vs ze

co

pron
  • they (singular). Gender-neutral subject pronoun, coordinate with gendered pronouns he and she. 

  • them (singular). Gender-neutral object pronoun, coordinate with gendered pronouns him and her. 

ze

pron
  • a gender-neutral third-person singular subject pronoun, equivalent to singular they, and coordinate with gendered pronouns he and she. 

noun
  • The name of the Cyrillic script letter З / з. 

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