You should be aware that permanently deleting Zynga Poker from your Facebook account will delete all previous progress you may have made on the game. If you choose to start playing the game again in the future, you will be required to start up from scratch. With this in mind, you may want to consider just hiding notifications from the application on your 'wall', as opposed to completely deleting it. This will disable posts and notifications from Zynga Poker, but won't delete all of your progress and saved data on the game, meaning you can resume your activities from where you left off at any later point.
If you have security concerns about Zynga Poker or are receiving any form of spam from the application, you should get in touch with the Facebook Customer Service Team as soon as possible. Alternatively, you can click the 'Report Abuse' tab next to any notifications from the application on your wall, and Facebook will deal with this as appropriate. If the problem is that your application t is faulty or broken, you can be rest assured that it can be restored - again, contact Facebook's Help Team for more assistance with this.