Is it permissible to perform prayers silently at work, knowing that prayer time is counted as part of one's wages, or should they be delayed and combined with Maghrib prayer?

It is not permissible to abandon prayer under any pressure, for it is an obligatory duty and the pillar of the religion. Every prayer must be performed at its appointed time, even if discreetly, and this is not considered theft. The employer's condition to abandon prayer is religiously invalid. If the employer insists on preventing prayer and you are unable to perform it, you must seek another job that allows you to pray.