The phrase "a challenging combination of" is correct and usable in written English.
It can be used to describe a situation or set of elements that are difficult to manage or integrate together.
Example: "The project requires a challenging combination of creativity, technical skills, and teamwork to succeed."
Alternatives: "a difficult mix of" or "a tough blend of".
He had a slow start to the session, dialling himself into the new 5.5km track, which combines a challenging combination of a fast first sector, a long straight and a twisty final sector.
The great diva Maria Callas recorded the role, that demands a challenging combination of singing, dancing and acting skills, but never performed it on stage.
Other courses (like the one we were on) are marketed as canopy tours, designed with a challenging combination of swaying sky bridges, cable traverses and zip line pathways cut through the deep forest.
Standouts like Evac, Exodus, Stronghold and Breach, provide a challenging combination of long sight lines and claustrophobic choke point chambers, often with gruesome central courtyards where multiple overlook positions guarantee tense, explosive stand-offs.
He banged inside with the likes of Corliss Williamson and Ben Wallace, attached himself to point guard Chauncey Billups more than once, and clamped down on Prince, a challenging combination of size and skill.
She does it with rigid portion control and regular, intense exercise — 45 minutes to an hour a day, Monday through Saturday, doing the Beachbody programs, a challenging combination of strength training and cardiovascular exercise.
After the Revolution of Dignity Ukraine has faced a challenging combination: Hybrid war from Russia side and economic and institutional collapse.
"My sense is that we have an incredibly complex and challenging combination of short-term and long-term-range challenges to face.
It uses a secret chemical formula to help the resins hold together fiberglass even under challenging combinations of heat and corrosiveness.
However, many of their applications rely on discrete devices to attain challenging combinations of ultra-low-loss performance (ultrahigh Q) and resonator design requirements.
