I wrote a long answer, but I’ve changed my mind about what I want to say, and now I’m too tired to write that. so here’s the first part.
Smartlife recently dropped its Ifttt integration after Ifttt raised the price is that it charges the manufacturers. So at present there is no way to integrate your SmartLife switches with smart things except by using Alexa as an intermediary. And that’s only a one-way integration. So it works pretty well for plug-in pocket sockets: you can have smartthings tell the pocket socket to turn on and off.
But that method doesn’t work very well for light switches, because while you could have smartthings tell the smartlife switch to turn on, if someone turns the smartlife switch on at the wall, or even via Alexa, smartthings won’t know about it. 
So I don’t think you can get to where you wanted to be in this case.
Technically, you would be fine just using these accessory switches as they are in terms of the wiring, but the problem is that they are very old devices and use zwave classic, not zwave plus, and they depend on Z wave direct association, which changed a lot with zwave plus.
So while you can add it to your smartthings Z wave network, at this point I don’t think the hub will recognize its button presses unless you happen to have an early release V1 hub. That is, unless the hub is also Zwave classic.
Combine that with the out of sync issues and I just don’t think it’s going to work well for you. It would be OK as an accessory if your master switch was a nearby Z wave switch so the accessory talked directly to the other switch rather than to the hub. But as it is, it just doesn’t seem like a good fit.