The phrase "a very difficult job to" is correct and usable in written English.
You can use it when describing a task or responsibility that is challenging or requires significant effort.
Example: "Completing the project on time was a very difficult job to manage, given the tight deadlines."
Alternatives: "a highly challenging task to" or "an extremely tough job to".
"They have a very difficult job to do".
He is doing his job but he has a very difficult job to do.
"Kabul Bank was a very difficult job to do and it made our life very tough," he said, referring to political pressure on the Central Bank.
"This has been the most rewarding, challenging and important job that I've ever done," Ms. Roche said, "and a very difficult job to leave.
"It's a job I love, but like many women I find it's a very difficult job to balance between all your family demands.
Our players are in good spirits and it's important we go there confident but clear in our minds that we have a very difficult job to do there".
If Penn State had lost today, Paterno said, "it would have been a very, very difficult job to convince them they are good".
When we have volunteers who are taking time out from their families, from their loved ones and so forth, to go over there because they have a very particular expertise to tackle a very difficult job, we want to make sure that when they come back that we are prudent...[because if we are not] we're just putting another barrier on somebody who's already doing really important work on our behalf.
"Being governor is going to be a very difficult job, as opposed to the 1990's, when it was an easy job".
"One of my core principles when I took the job was to always respect the officials - they have a very difficult job - and to try and act with dignity, to never confront a referee or show that indiscipline during a game.
"They bitterly regret the death of Mr Mubenga but have always said they were trying to do a very difficult job in difficult circumstances to the best of their ability," lawyers for the three men said in a statement.
