Zoo Game

You are playing a game with friends. This game requires entering a word that consists of $x$ and $y$ that denote the number of $Z$s and $O$s respectively. The input word is considered similar to the word zoo if $2*x = y$. For winning the word needs to be similar to the zoo. For your reference, consider words such as 'zzzoooooo' and 'zzzzoooooooo' are similar to the word zoo but not the words