The phrase "challenging difficulties" is correct and usable in written English.
You can use it when you want to describe a situation where there are difficulties which require an effort to overcome them. For example: Facing the challenging difficulties of the economic crisis, the government took measures to protect local businesses.
With patience, we exhibit forbearance under strain, especially when challenging difficulties end up becoming longer-term.
Although much progress has been made for the time-delay systems in the adaptive control field, some challenging difficulties still remain.
In noisy and reverberant environments, the problem of acoustic source localisation and tracking (ASLT) using an array of microphones presents a number of challenging difficulties.
In particular, the use of Dempster Shafer theory of evidence within Markov models has brought some keys to several challenging difficulties that the conventional hidden Markov models cannot handle.
Indeed, they do not find challenging difficulties in accessing unskilled and semi-skilled manual jobs, as they experience in self-employment and non-manual jobs (Fullin and Reyneri 2011).
But for me, these Portuguese vines, many of them so old, yet still so remarkably fine, present the most challenging difficulties of them all...simply because of where they are.
Rignall called the game's graphics "stunning, with beautifully drawn scrolling forced perspective 3D backdrops and some great sprites"; he also lauded the game's playability and simple controls, challenging difficulty, and overall fun factor.
Challenges, difficulties and barriers to environmental engineering applications needs to be readdressed and reenvisioned.
"There will certainly be challenges, difficulties and setbacks along the way," Mr. Walcott said, "but I am confident that by working together, we will come out stronger on the other side".
However, ART has not been without its challenges, difficulties, and failings.
"Working this way presented many creative challenges, difficulties and long-awaited solutions".
