title: zsh: How to test for existence of two programs on zsh use $+commands
body: <p>In zsh we can test for the existence of a progragram using this:</p>
  <pre><code>(( $+commands[program] )) &amp;&amp; program
  </code></pre>
  <p>My question is: How to use <code>commands</code> for testing the existence of two programs instead one?</p>