The phrase "a complex challenging and" is not correct as it is incomplete and lacks clarity.
It can be used when describing something that is both complex and challenging, but it needs to be structured properly within a complete sentence.
Example: "The project is a complex, challenging, and rewarding endeavor that requires teamwork and dedication."
Alternatives: "a difficult and intricate" or "a complicated and demanding".
It is a complex, challenging, mysterious and deeply intelligent piece of cinema and I very much agree with Xan Brooks's judgement that "Winter Sleep shows Ceylan to be as psychologically rigorous, in his way, as Ingmar Bergman before him".
The first was that art making is a far more complex, challenging and thoughtful endeavor than he (sheepishly) thought it was.
The stabilization of equilibria in chemostats with measurement delays is a complex and challenging problem, and is of significant ongoing interest in bioengineering and population dynamics.
Dr David Bennett, chief executive at Monitor, said: "The TSAs have been set a complex and challenging task and, while any delay is frustrating for patients and staff, it is important to get it right for local patients.
Yet the Tunisian people came through a complex and challenging process and achieved important results -- results that can provide the foundation to confront a long legacy of human rights abuses and pave the way toward a democratic transition built on the rule of law and trust between citizens and the state.
The result is both a celebration of mothering and a complex and challenging investigation of just what and who we are and become when we create children.
At a macro level, a number of studies have shown that the diagnosis and treatment management of meningitis is a complex and challenging problem for government and healthcare agencies requiring novel approaches to its management and intervention [ 11- 14].
Controlling the motion behaviors of nanoelectromechanical systems (NEMS) and nanorobots is a complex and challenging issue due to surface and interface effects.
So we have a complex and challenging landscape of attitudes, behaviors and perceptions with parents and teens negotiating this constantly changing world of devices, apps, social media sites and services.
