Zokotl was mention in "The Widening Gyre". Tyr Anasazi is trying to boost Seamus Harper's survival desire by describing his enslavement and escape on Zokotl, where he was forced to work the diamond mines.
Harper: Hey, do me a favour, will you? Talk to me about something. Take my mind off things.
Tyr: You want a story? All right. When I was sixteen, after I'd lost my family, I was captured by slavers and sold to the diamond mines on Zokotl. One day while working in the mines, I noticed that the main support for my section had rotted through. I pointed it out to the overseers, but instead of fixing the problem, they cut my rations and doubled my work shifts. A week later, the ceiling collapsed, burying me alive two hundred meters under ground.
Harper: Thanks! That cheered my up.
Tyr: It should've. Because I lived. I clawed my way out over the bodies of the dead. I escaped into the desert. I lived on seep water and sand rats for an entire season. And then, one night after I'd healed, I visited the overseers and thanked them for their conscientious attention to worker safety. So, don't you tell me that I'm going to die here today, because the sun has not yet risen on the day when Tyr Anasazi, out of Victoria by Barbarossa, will face death graciously. I will kick, and claw, and bite, and scratch, and spit my last breath in its face, and as long as you are with me, you will do the same. Is that clear? Is that clear!