Can You Do Wudu with Hijab On?
Question

I work in a company and it is difficult to do Wudu for prayer (i.e., to take off the Hijab in order to wipe my hair and ears).
My question is:
Is it better to wipe over the Hijab and wipe the ears as much as possible only? Or should I combine Zuhr and `Asr prayers at home?
Praise be to Allah.The Challenges of Wudu in a Mixed Workplace
It seems that it is difficult for you to take off your Hijab because of the presence of non-Mahram men in your workplace. If that is the case, then you should note that mixing of women with non-Mahram men leads to many negative consequences, such as being alone with or looking at a member of the opposite sex, speaking softly, temptation, and other things that are no secret to people of insight.
Maintaining Modesty While Praying at Work
If a woman is faced with this problem and the time for prayer comes whilst she is at work, and she cannot delay it until she goes back home, then she should pray in the most concealed place in her workplace, covering her hands, face and all of her body in front of non-Mahram men.
The Difficulty of Wudu with Hijab On
Your saying that it is difficult to take off your Hijab in order to wipe your hair and ears when doing Wudu makes us wonder: how do you wash your arms and feet in the presence of men?
You must be aware that the arms and feet are part of the `Awrah which must be concealed from non-Mahram men. As for the face and hands, there is some difference of scholarly opinion, but the most correct view is that they must also be covered.
Wiping Over the Khimar during Wudu
It is permissible for a woman to wipe over her Khimar (head cover) in the case of necessity, such as when it is very cold, or it is difficult to take off her Hijab and put it back on.
Shaykh Ibn `Uthaymin (may Allah have mercy on him) was asked: Is it permissible for a woman to wipe over her Khimar?
He replied:
The well-known view in the Madhhab of Imam Ahmad is that she may wipe over her Khimar if it goes under her chin, because it was narrated that some of the womenfolk of the Companions (may Allah be pleased with them) did that.
Whatever the case, if there is some difficulty, either because the weather is cold or because it is difficult to take it off and put it on again, then there is nothing wrong with wiping in such cases, otherwise it is better not to do that.” (End quote from Fatawa At-Taharah, p. 171)
It says in Sharh Muntaha Al-Iradat (1/60): It is also valid for a woman to wipe over a Khimar that goes under the chin, because Umm Salamah used to wipe over her Khimar, as was mentioned by Ibn Al-Mundhir. (End quote)
So long as the Khimar covers the ears, it is sufficient to wipe over the Khimar and there is no need to put the hands under the Khimar to wipe them. Similarly, if a man is wearing a turban, he does not have to wipe his ears too, even if they are not covered; rather that is recommended only.
Shaykh Ibn `Uthaymin (may Allah have mercy on him) said: “It is also Sunnah to wipe whatever part of the head is uncovered, such as the forelock, the sides of the head and the ears.” (End quote from Fatawa At-Taharah, p. 170)
Striving for Piety and Obedience in the Workplace
A Muslim woman must strive to fear Allah and obey His commands, and avoid that which He has forbidden, and keep away from working in mixed environments, which may earn her the wrath of Allah. She should beware of giving this world precedence over the Hereafter, for it is transient pleasures, but what is with Allah will never fade away. It is narrated in an authentic report that our Prophet (peace and blessings of Allah be upon him) said: “Whoever gives up a thing for the sake of Allah, Allah will compensate him with something better than it.” (Classed as authentic by Al-Albani in Hijab Al-Mar’ah Al-Muslimah, p. 49)
We ask Allah to help you to do what is best for you in this world and in the Hereafter.
And Allah knows best.