Linking two Z-Wave Switches to mimic each other on different electrical circuits but same hub

I have existing three way exterior flood lights on a legacy three way switch. I have a new samsung smartthings hub and a GE outlet connected for my pool pump.

I wanted to add another flood light to my shed; however, I don’t want to dig up the driveway to run the romex…I wanted to see if I could somehow install a z-wave three way switch (to replace existing) and if it would need both switches to be on z-wave - and if I could like another so that when I turn one light on all three lights come on - not having to issue voice command to my google hub

That’s a very common set up with smartthings. It’s called the “mirror“ function.“ Or a “virtual three-way.“ The two switches can be any protocol as long as each can communicate with the smartthings hub. Then the first switch sends a message to the hub and the hub sends a message to the second switch. They don’t have to be on the same circuit. In fact, one of them can even be battery-operated.

The mirror function is part of the official “ Smart lighting” feature. To get to it tap on the three horizontal line menu in the upper left, then Smartapps, then choose smart lighting.

When you set up the automation, one of the options will be “mirror.“

You can use two automations and have each switch mirror the other as well. That way when one switch turns on, the other also turns on. And when one turns off, the other also turns off. That keeps them in sync in your app. :sunglasses:

Which switches do I get any three way smart? Do all three need to be smart switches or one on each circuit?

Thanks very helpful