The phrase "a difficult and lengthy" is correct and usable in written English.
It can be used to describe a task, process, or situation that requires significant effort and time to complete.
Example: "The project turned out to be a difficult and lengthy endeavor, requiring months of research and collaboration."
Alternatives: "a challenging and time-consuming" or "a hard and protracted".
Reversing the effect is a difficult and lengthy process.
Christian was instead a sensation, breezing through a difficult and lengthy solo.
But Johnson & Johnson executives say that identifying the root cause of the problem was a difficult and lengthy process.
However, arranging curriculum is a difficult and lengthy task which enterprises traditionally devote a large amount of human and material resources to.
Building a course timetable is a difficult and lengthy task which universities devote a large amount of human and material resources to every year.
However, Zhuang Guotai, the head of the MEP's Department of Nature and Ecology Conservation, has said that cleaning up soil pollution is a difficult and lengthy process that will require huge investment.
Come to the hospital prepared to capture memories with your baby and to nurture yourself and your partner through a difficult and possibly lengthy delivery.
A senior US government official also played down expectations, saying it would be a "complicated, difficult and lengthy process".
A subsequent investigation by the British Bombing Research Mission concluded that the entrances had been heavily blocked and that it would be a very difficult and lengthy engineering task to reinstate them.
It can be a very difficult and lengthy process, but it's so important that we are there for these children to help them find their true identities and rediscover that feeling of being part of a community.
Hours later a senior U.S. administration official also played down expectations, telling reporters in the Austrian capital that it will be a "complicated, difficult and lengthy process" and "probably as likely that we won't get an agreement as it is that we will".
