As above, but most of the time I just pick them off for giggles. Don't take them lighly but the best thing to do is jink heavily. As with any sim, the bullets are aimed either by eye or by the Gun Dish on the Shilka. The more you maneuver, the harder it is for them to hit you, simply put. As for targeting... hit E until the ZSU is targeted, and hit F4 for padlock, and if it's the one you want, learn how to maneuver your a/c until you get within a few degrees (Mavs can sorta offboresight, but my EELs are great for that ) launch and pull away, and if you hit it, the view will return to center. If there's no SAM threat then go high and pick them off.