What is the ruling on an employer preventing an employee from performing the obligatory prayers (Dhuhr, Asr, Maghrib, Isha) during working hours, and is it permissible for the employee to combine them and perform them after work?

Delaying prayer beyond its prescribed time without a valid excuse is a major sin. Allah Almighty says: "So woe to those who pray [But] who are heedless of their prayer." (Quran 107:4-5), and heedlessness here means delaying it beyond its time. Work is not an excuse for abandoning prayer or delaying it. Allah described men whom neither trade nor selling diverted from the remembrance of Allah and the establishment of prayer. Therefore, one must request time for prayer from the employer, or leave the job that prevents performing it on time, for whoever abandons something for the sake of Allah, Allah will compensate him with something better.