i feel its not like kabir is not interested in zara but the other way round .zaraa consider kabir very low and kabir is introvert has crush on zara and doesnt know how to handle woman like zara as he cant missbehave with her
so i feel kabir is afraid to take first step even if he want because of fear that what zara will missunderstand him and will do war of words so he just take precaution
thats why when kabir has to feed he showed no interest so that zara not missunderstand but suddenly when zara played the game from her side and took some interest from her side kabir suddenly opened up
i feel in first stage this will happen only kabir will try to not show zara that he like her or has crush but zara one move and kabir will take further moves
in the second when he started to to take interest rukshar came unknown to him he totally unobilivious of the fact that rukshar touched his hand or ate that kheer as he was just busy showing and gazing zara that he is even interested and this is how rukshar will somehow try to enter and zara will notice all this and when zara made him eat he grabbed her hand forcefully and hurt her because ruksshar missunderstanding will make him do so and he will even hurt zara by mistake only
but later part zara not let rukshar in and will be carefull the very next time and even kabir will know somewhat of rukshar interruption and he will let zara win but zaa when made kabir eat that she didnt let him eat means she will not accept him or let him overrule till he accept and try to know the difference of right and wrong