Is it permissible for the recipient to continue taking the Zakat amount he receives from his employer, considering it part of his salary and his unfulfilled rights, and does the sin fall upon the giver alone or also upon the recipient if he knows it is from Zakat, and what should he do with the amounts he previously took based on this interpretation?

It is not permissible for the employer to oppress the employee or withhold his wages. If the two brothers prevent you from receiving your agreed-upon rights, it is permissible for you to take them from their wealth without their knowledge, through the method of "al-Dhafr" (taking one's right when denied by the obligor). However, taking from zakat funds is not permissible if you are wealthy, and you must return what you have taken from it. If you fear harm, then give it as charity to the poor.