Acrozilla and AcroChallenge have much in common - and some significant differences, too.
This page highlights those differences.
Differences from Acrofever page.

How Acrozilla Differs from Acrochallenge

    New, improved features:

  1. Easier to find a mistake in your acro as the letters turn green when matched.
  2. Never more than 2 of any letter in the acro letters.
  3. If yours is the only acro in the round, you can win points even though it was impossible for you to vote.
  4. All games visible in the lobby, without any intermediate levels.
  5. Ability to stay in a room in non-playing mode to avoid holding up the game.
  6. Games are paused if there are no active players (only watchers).
  7. Simpler private message syntax: @player rather than /pc player\ (because spaces not allowed in player names). The Acrochallenge syntax is accepted though.
  8. You can reply to a private message (or follow up one you sent) by clicking it.
  9. Clicking a players name in the score list sets up a private message.
  10. /games command or clicking an icon shows you all the active games in a popup graphic rather than chat lines (and you can join one of those games with a click).
  11. You can see your own acro during voting (but still cannot vote for it).
  12. For non-voters, the number of votes they received is displayed (along with 0 points).
  13. Support for Story Time games: Title round and default "Continue the story" topics automatically supplied, as are Story recaps.
  14. Support for Topics by Creator: can preload a whole set of topics after game is set up.
  15. Logging of scores and acros, for, say, a league table.
  16. Recognition of more high scoring acros ("Double Digit Club" vs player's highest scoring acro shown in profile).
  17. Different scoring: Bonus points are based on the number of votes received rather than the number of letters/words of the round.
  18. Simpler process for creating a game, with fewer options.
    All games are 10 rounds, and maximum players is 12.
    No faceoff option provided.
  19. A broader range of Server-supplied topics, with date-based additions for holiday seasons.
  20. Simpler re-submit process for acros: Just edit and hit Enter.
    If you want to take back an earlier entry, there is a "Revoke" button.
  21. If you return to a game after a disconnection, you keep your points.
  22. Less likelihood of disconnection in the first place.
  23. Ability to have online moderators who can deal with troublemakers effectively.
  24. Room creator can /boot a troublemaker and keep him from returning.
  25. Sounds to indicate start of round, acro submitted, and 10 seconds of acro time left. Option to turn them all off (collectively).

A few things AC has that AZ lacks (for now at least).