Replacing 3-way switch with new ones
To move a 3+ way switch to a Zwave system, you will have to replace all the switches that control the light.  From the picture, it looks like what you have is the 3 way switch at the end of the switch run, meaning the red and white are the travelers and the black is the common here.  So that means the other switch (lets call it the main switch) will likely have the line /2 wire, the load /2 wire and the 3 way /3 wire that comes to the box in your picture.  If thats not the case, please notate that.

I did a similar setup last week with Jasco/GE switches.  I checked the installation sheet for this one and it is very similar.  So, the new z wave switch (at the main switch)will have 4 wires going into it.  The black wire from the line, the black wire from the load, a white wire (which will connect to all other white wires) and the red wire from the /3 connecting to the traveler connection.  Go ahead and put a wire nut on the black wire from the /3 wire, it wont be used any more.  Also connect up all of the grounds, and connect that to the switch.

At the other switch (the one where the picture is), connect the white wire to the common and the red to the traveler.  Put a wire nut on the black wire, its no longer being used.  Connect the ground wire to the switch.

With that, you should be good to go.