oh fuck I just realized I haven't babbled about my personal headcanon/theory of Sohreh and Zandik's relationship on here yet. And since it's possible we could be getting new Dottore lore next week, I should probably drop this now in case it gets completely debunked lol
I actually have two routes for this cuz I also like the theory that he was framed for her murder. And I love adding more angst and turmoil onto my pookie.
Basically, I think that Sohreh had a big fat crush on Zandik and unironically said to herself "I can fix him." And I think she would have succeeded...
if she had met him sooner in life.
But I think by then, Zandik was already too far in his own head. He'd lived his whole life up to that point being shunned and ostracized from everyone else. So, why was this random Amurta Dastur trying so hard to start up conversations with him? How annoying...
But Sohreh was determined and stubborn. Sure Zandik was cold and rigid in his thinking, but she still never liked how everyone else treated him. Surely it wasn't healthy, even for a genius like him, to be so isolated and alone.
She realized real quick that Zandik had zero interest in small talk and was just as stubborn as her. But Sohreh was known among her peers for having a contagious friendliness to her and a knack for getting people to loosen up.
Slowly but surely, she managed to pry open the door to Zandik's heart by using the subjects that he was interested in to keep him talking. And Zandik slowly but surely found himself starting to open up to her.
However, this terrified him.
Why was this girl trying to get him to just... talk and hang out with her? Why was she being so kind and patient with him? But more importantly, why was it starting to work? He was supposed to be cold and shut-off, to keep others away. No one liked him. No one was supposed to like him. He was supposed to be alone. No one else could be trusted.
Until canon proves me otherwise, I will hold the belief, that super deep down in the darkest depths of Zandik's heart, he genuinely liked Sohreh—maybe even reciprocated her feelings. But he hated that that was the case. It meant that there was still a part of him that wasn't cold, and still very very human. For him, that was a threat.
So, if Zandik did kill Sohreh with his own hands, I think it was partially out of fear and anger that this random girl made him feel vulnerable and loved of all things. She had to go. And since she trusted him so wholeheartedly, it was easy for him to dispose of her.
If he didn't kill Sohreh, I think that, after lots of internal struggling, he actually decided to listen to that terrifying voice in the back of his head telling him to just... accept her kindness. And befriend her.
But when Sohreh died and her death was put on him, that was it for him. That tiny little bit of warmth, vulnerability and hope she had given him completely evaporated. This was all the proof that he needed that he was never meant to be loved or live a normal life. Sohreh approaching him had just been the gods' way of mocking him.
Regardless of whether he killed her or not, I believe that current Dottore's thoughts when thinking about Sohreh could be summarized with:
"I hate [that I miss] you."