The phrase "a complex and risky" is correct and usable in written English.
It can be used to describe a situation, decision, or action that involves both complexity and a degree of risk.
Example: "Investing in emerging technologies can be a complex and risky endeavor, but the potential rewards are significant."
Alternatives: "complicated and hazardous" or "intricate and perilous".
What a complex and risky work this is.
With today's missile launch, North Korea was issuing a reminder that maintaining peace and stability in this part of the world is a complex and risky game.
I wonder whether her political masters would agree with her? Indeed, there seemed to be a consensus among most of the speakers that putting out a tender is a complex and risky business.
In several cases, OOS requires the capture of orbital objects, which is a complex and risky operation that can be successfully performed by robotic manipulators.
Given that MBS rules with absolute authority, the CIA concludes that such a complex and risky operation ― involving 15 agents flying on government aircraft to execute a perceived enemy at a Saudi consulate on foreign soil ― would proceed only at MBS' specific direction.
Evolving modern medicine places patients in a complex and potentially risky situation that combines invasive procedures capable of delivering microbes to naturally sterile tissues and organs, together with iatrogenic immunosuppression that severely dampens resistance mechanisms to infectious agents.
The discovery and development of a new drug to treat cancer is an enormously complex and risky undertaking.
Aging is widely regarded as a time of cognitive and functional decline, yet in the midst of the challenges of aging, older persons are confronted with a host of complex and risky decisions that arguably have as much (if not more) significance as decisions made earlier in life.
Even among those who do, only those with money to burn would be in a position to jump into investments so complex and risky that the world's major banks utterly misjudged them.
Even a no-flight zone, he said, would be complex and risky, since American warplanes would first have to destroy Libya's air defense systems.
It says the ban means a woman seeking a second-trimester abortion would instead have to submit to more complex and risky medical procedures.
