The phrase "a difficult and laborious" is correct and usable in written English.
It can be used to describe a task or process that requires significant effort and is challenging to complete.
Example: "The project turned out to be a difficult and laborious endeavor, requiring countless hours of work."
Alternatives: "arduous and challenging" or "strenuous and demanding".
Unfortunately, the activity-based purification of unidentified proteins from serum has proven often to be a difficult and laborious task.
Why embark on such a difficult and laborious journey?
For example, the unit "When I have to walk up and down the stairs, I move up the stairs in a sitting position and then I'm very short of breath" was interpreted in the following way: "Going up the stairs is a difficult and laborious exercise, which causes shortness of breath".
It's because it's so hard, in the "pointlessly-difficult-and-laborious-surely-this-can't-have-been-the-intention" sense.
Research has shown that the implementation of integrated care is a very difficult and laborious task [ 66, 67], especially regarding the proposed model because it focuses on integration across the entire continuum of care for all frail elderly.
Determining the fitness of viruses in a population is experimentally difficult and laborious, because individual virus particles need to be isolated and analyzed separately.
It it is more difficult and laborious to shape a dolphin from example hematite than only polish a hematite stone in its original shape.
Vaccines work by stimulating the immune system to ward off infections, yet progress on an effective HIV vaccine has proven to be difficult and laborious, according to Dr. Nicholas Hellmann of the Gates Foundation's HIV, TB and reproductive health program.
However, expression of proteins in alien hosts is often a difficult and time-consuming task, requiring laborious screens to identify the optimal expression organism (or strain) and experimental setup.
This aspect of the study could also be considered a negative point by others because of the so-called difficult and laborious purification and the need for special equipment.
