It is not permissible to delay the prayer beyond its time because of work as work is not an excuse for delaying prayer. Zuhr and ‘Asr and Maghrib and ‘Isha prayers are the ones that can be combined (in some cases). But you cannot join `Asr and Maghrib. So you must organize your time at work in a way that will not interfere with your performing the prayers on time.

It is permissible for a sick person to join prayers, so he may join Dhuhr and `Asr, and Maghrib and `Isha’, at the time of the earlier or later prayer, depending on what is easiest for him. Difficulty caused by sickness is one of the excuses which make it permissible to join prayers.