title: tmux zoom in or out without toggle
body: <p>tmux's zoom (<kbd>&lt; prefix></kbd> + <kbd>z</kbd>
   or <code>resize-pane -Z</code>) is a toggle.</p>
  
  <p>How do I zoom out (restore) <em>only</em> if the current pane is already zoomed in?</p>
  
  <p>How do I zoom in (maximize) <em>only</em> if the current pane is un-zoomed?</p>