May be tippy because the pad under it is not level and it sure looks like there was not enough fill around it to keep it from washing out.
Those pads are alright for flat surfaces, but I always preferred to poor a concrete pad if there was any slope at all. Most hvac contractors won't go to the trouble, though, as you need to form and poor the concrete a few days before setting the unit down on it, and can't drill into it for 7 days (if my memory serves me). I don't think those pads will stand up to being drilled into for anchors. I think it would take a hell of a wind to blow the unit over, although those columns you have under it change its centre of gravity.
Go back and add your location to your profile.
It was installed to close to the house. Should have been out behind the drip ole of the roof.
You can't anchor to a plastic pad, not to mention anchoring is not going to solve the ground shifting. You need concrete or you need to level the ground under the unit, pack it down.
Your concern is to secure the unit from rocking/ moving in high winds.Can you elaborate? Do I wrap it around the top of the unit securing it at two places to the wall? Would you drill new holes or existing screws that hold the unit together?
In other words,Don't use that strapping it looks like crap, you wouldn't like the look and you will have to drill into your house. Have never seen anything like that in the field. If you really think you have to anchor it down you can go right through the inside of the unit down through the 4 legs into the concrete pad after the pad is changed and the unit is back level and in place. You really shouldn't have to anchor it.
In other words,
Hire a HVAC guy to do it and not do it yourself.
Replacing the pad would require disconnecting the unit.
So spend 500 for the pad or 20 bucks on some strapping.
Level the pad and mud jack until all the cavity underneath the plastic is full.
Not unless you have all the hvac tools to properly do it you're not. The true and proper way to do it is to remove/disconnect the unit and move it aside. Other than that you can pry up the unit and set bricks or dirt under there but without a build up and hard pack of the dirt you'll still be playing Russian Roulette.A "HVAC guy" did this in the first place. I'm going to fix it.