So this is what I do....
a) Set up Sekonic 758DR as master trigger
b) Set up Pocketwizard Plus III as a receiver with a N3 Output cable and connect it to my Canon to trigger it
c) Set up my ST-E3-RT in the hot show as the master and have it trigger by 600EX-RT's as slaves.
Had to buy one PW receiver (could have bought the less expensive Plus X and used it as the receiver but I had reward offer on Amazon so I spent the extra $50 to get a receiver that could also support groups with the 758DR if I wanted to.
Now also have the ST-E3-RT working as an off camera master to trigger my on camera 600EX-RT so might just use that and not have the PW +III do that job.