I seem to recall reading in Voyages of the Imagination that The Left Hand of Destiny was itself delayed for quite some time by J.G. Hertzler having trouble putting everything together, leading Marco to bring Jeffrey Lang to the party as co-writer.
Correct. In fact, I broke that news. We had Mr Hertzler here in Sydney for a convention and, for my from-the-audience question, I asked him about the seemingly delay in his books coming out. He was thrilled that I'd even heard about them, and he told the anecdote about how he "wasn't as clever at novel writing" than he'd originally assumed, and how Marco
had recently come to the rescue by bringing in Jeffrey Lang to give his work an overhaul. The duology missed the originally-intended publication dates by about a year.