I think they can both be blamed for what they're doing but for them they think it's the right way, not everyone has the same way of thinking and not everyone would deal with a situation in the same way.
Aditya is running out of time he only has a few days to convince Zoya so he's becoming impulsive like he was at the very start not thinking about the consquences. He seemed to realise what he was doing after Zoya pleaded with him to stop. He's done the same prank before and knew what would happen but he must've felt like had no other choice, why else would she leave? For him it's all or nothing he has to put everything he has into this, it doesn't matter if he makes a fool of himself or loses his self-respect because he is stopping Zoya from making a mistake and finding a reason to keep 'living'.
Zoya is trying really hard to block out her feelings and the last few things Aditya said to her made her realise that Aditya knows how she feels. She is not thinking about the consequences either like when she wanted to reopen the case she didn't think about what would happen to Aditya or herself. She has been shown before that when she's dealing with something she doesn't pay attention to other like at the start when Noor was trying to talk to her about her dad wanting to get her married she wasn't really paying attention. She's now at a point where she's trying to prove herself right but at what cost? She's not listening to anyone. She's scared to be in love so has taken the safe option because if Arshad did do anything she wouldn't be hurt.
She is playing a game, she's only thinking about now and not the future, and Adi is thinking about the future and not what his actions are doing now.
Arshad doesn't help lit seems as if he's deluded and genuinely believes that Zoya will love him, she's told him before that she doesn't love him and can't he see that she'll always choose Aditya over him. She left her engagement. He's allowing her to play with them.