Use this:
Those types of zwave modules control 2 lights so you can control 2 lights from a single gang box or even 4 from a dual gang. Anymore than that and you're not going to fit anything into the box. You'll need a box extender for those outdoor boxes. You can also use metal boxes with zwave, I know because I am doing it.
Make sure whichever module you buy is Zwave Plus
Im 130 feet from the residence, which has radiant barrier in the walls.... and some foliage on the way.
I guess I can mock up a metal box and see if it will work, but much of what I read seems to tell me it wont be happy.
edit: Thought you were saying use one or the other- see now it was 'use a standard double/duplex swithc AND a dual channel module... got it. At first I thought it was a duplex zwave switch.
(I have a fall back of placing a repeater module in one of the path lights- provide power to the module, and its sole role would be to repeat the signal since the path lights are controlled elsewhere. Ive got about 3" of PCV cap out of the ground that could hold a module like you posted...Hopefully not needed.)
The duplex switch is a very good solution- one of those and a standard switch give me 3 switches in a two gang
thx