The phrase "a complex challenge and" is correct and usable in written English.
It can be used when discussing a difficult task or problem that requires careful thought or effort, often as part of a larger sentence.
Example: "The project presents a complex challenge and requires innovative solutions from the team."
Alternatives: "a difficult task and" or "a multifaceted problem and".
Johnson writes: "Raising university participation rates is a complex challenge and it is, of course, not one that universities alone can solve.
"But stopping work and how you go about it is a complex challenge, and I thought I should stop while I was still enjoying it and while I still have time to do other things".
"Doping in sport is a complex challenge and I think we need to expand the fight and our dialogue beyond new rules and the number of doping control tests carried out," he said.
This is a complex challenge, and solving it will require a range of approaches as well as the collaboration of governments, NGOs, academic institutions, for-profit companies and philanthropic organisations.
While our systems get better over time, counterfeiting remains a complex challenge, and we keep investing in anti-counterfeiting measures.
Skin regeneration and tissue engineering methods remain a complex challenge and offer the possibility of new treatment for injured and burned patients.
Thinking such a complex challenge through, and executing it, is Murphy's strength.
Decarbonising the built environment cost-effectively is a complex challenge public and private organisations are facing in their effort to tackle climate change.
However, this particular type of rock has a number of features that make it a complex challenge for characterization and management of an oil field.
Those [of us] who are expected to monitor religious trends have reason to find talk of blasphemy a complex challenge to commentators and responsible citizens.
This is why inclusion is such a difficult, complex challenge, and yet, such a necessary one to address on a continual basis, with increasing sophistication and determination.
