I need help with a Zooz zen 71 switch.
I have a typical 2 gang box. Switch on the left controls the light, switch on the right controls the fan.
I want to replace the switch that controls the light with the Zooz.
How in the world do I wire it?
In the box there is one 14-3 Romex and (2) 14-2 Romex.
I thought I knew what I was doing so nothing is currently connected.
I have a request in for Zooz support but hoping I can get a faster answer here.
It’s a little bit hard to see the wires in the picture due to the shadows! It looks like a black & red wire on the left, a black wire in the middle, and another black wire on the right–is that correct? Also, was there a wire jumper between the two switches when you removed them?
Typically, the fan is wired these days with the 14-3 Romex: a black and red wire to the light & fan itself–but not necessarily in that order. My best guess is the other two black wires from the 14-2 Romex cables are power in from upstream and, possibly, power out to another outlet or switch elsewhere.
The white wires, all tied together, are the neutral. You’ll need to add a jumper from the neutral bundle to the ZEN71, as it requires the neutral connection.
Did you get any pictures prior to removing the switches?
Disclaimer: I’m not a licensed electrician! If you have any doubts at all, please consider finding an electrician to sort things out for you.
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You are correct. Black and red on the left, black and black on the right
Yes, they were jumpered together.
No I did not get pictures. I wish I had 
Probably the jumper between switches–probably a black wire–carried power from the source (one of the two black wires on the right) from one switch to the other, so they both have the line side of the circuit.
What is your level of electrical experience? Are you familiar with how you determine which black wire is the supply line using a voltmeter or a neon tester?
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Yes. I can figure that out. Just unsure of what wires go where on both switches
The diagram on the ZEN71 instruction sheet titled, “ZEN71 WIRING DIAGRAM FOR SINGLE POLE INSTALLATION” is pretty much what you need to wire the lamp control.
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One of the black/red wires on the left is what (probably) goes to the light or fan. You’ll need to figure out which one goes to the light and connect that to the Load side of the ZEN71.
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The black Line wire shown on the installation instructions is fed by the black jumper wire that originally came from the other switch, where it connects to the incoming line–and perhaps to the other black wire on the right that (presumably) goes to another switch box or an outlet somewhere downstream from here.
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The remaining black or red wire from the left hand side of the picture, coming from the 14-3 Romex cable is probably the fan itself. This connects to the Load side of the original, right-hand switch.
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And you will need a new white jumper wire from the neutral bundle (the white wires tied together) to go to the ZEN71 Neutral as shown on the installation instructions. I have usually found it easier to add the new white neutral jumper beforehand, when there isn’t the clutter of the other switches in the way!
Note the comment on the Installation Instructions that states, “Insert the ground (bare) wire into the Ground terminal (not shown in the diagram).” Probably the other switch has a ground connector, too. These should all be wired together to the bare ground wire. It is a safety ground and is generally required by current electrical code.
Again, be sure what you are doing and be careful! There are dangerous voltages present on those wires. Be safe! 
You made a good choice in the Zooz ZEN71. I have several myself and they work very well!
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THANK YOU!!!
I appreciate the help!
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Would it be safe to connect all the other black wires together under a wire nut and run a jumper to the line terminal on the old mechanical switch?
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If the previous assumptions of where the other black wire goes (presumably downstream to another outlet or switch) is correct, yes. That’s what I would do! 
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Were there no ground wires connected to the original dumb switches? It looks like all the ground wires are tightly bundled with no way to connect to the switches.
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