How is this conversation possible?

Question

"Kill him!" God yelled. "You hate him! He kept you in squalor, forcing you to fight for your survival as a child."

He made me strong, Zane thought.

"Then use that strength to kill him!"
_{The Well of Ascension: Chapter 18}

It is shown later in the book that:

"God" is Ruin speaking to Zane by virture of the spike in Zane's back

And in The Hero of Ages, we find out that:

Ruin can speak to someone's mind but not hear their thoughts, and Preservation can hear their thoughts but not speak into their mind.

So how is this conversation possible? Is there an in-universe explanation? Or did Sanderson make a mistake?

Answer 1

There's no word of creator I can find, and no power or cosmere related reason Zane's thoughts should be audible. So my speculation would fall back to the last possibility - the art of reading people and depth of experience.

Ruin cannot hear Zane's thought, but he can observe him and the world. Any gifted con artist with some familiarity with Zane would be able to tell - in general - what was bouncing through his head by watching him closely. Not only is Zane dealing with an entity very familiar with conning people, but one that has been observing him, personally, for a lengthy amount of time. An entity who has millennia of experience at the art of whispering thoughts, while using his senses for everything else.

Answer 2

In Annotation Mistborn 3 Chapter Fifty-Four Brandon Sanderson states:

Notice that Ruin’s voice doesn’t come to her until after she puts the earring back in. As she points out later, his telling her to kill isn’t as specific as she’s interpreting it. He’s just sending her a general feeling that she should kill and destroy; his attention is elsewhere at the moment, watching what Spook is doing.

Basically Ruin can broadcast 'kill that' and people will generally fill in the blanks as to what he's talking about.