The phrase "are enormously complex and" is correct and usable in written English.
It can be used when describing something that has a high level of complexity, often in a formal or academic context.
Example: "The systems we are studying are enormously complex and require extensive analysis to understand fully."
Alternatives: "are highly intricate and" or "are extremely complicated and".
The biochemical aspects of human metabolic diseases are enormously complex and rely heavily on modern technical and chemical advances for detection.
But the original hope that close study of the genome would identify mutations or variants that cause diseases like cancer, Alzheimer's and heart ailments — and generate treatments for them — has given way to realization that the causes of most diseases are enormously complex and not easily traced to a simple mutation or two.
Stem cell systems are enormously complex and 600 million years may not be long enough to reinvent another system from scratch.
This difference may not be significant since moving natural scenes are enormously complex and a much larger dataset of human gaze is needed for evaluating models of visual saliency.
They are enormously complex and multistep processes involving regulation at the post-transcriptional level of adhesive molecules, proteolytic enzymes, and cell growth and angiogenesis factors.
The argument over when and where and how to intervene is enormously complex and, fundamentally, unresolvable.
The present economic crisis is enormously complex, and any sound attempt to deal with it will therefore itself have to be enormously complex.
According to American and European investigators, the network that supplied Libya was enormously complex, and not all the paths led directly back to the Khan laboratory.
The task of carving out the new entity was enormously complex, and involved rewriting countless contracts with unions, suppliers, and creditors.
The takeaway: Collective intelligence among human animals is enormously complex and there are techical, semantic and collaborative challenges that stand to hold back progress if the community fails to remain aware.
Yet the global climate system is enormously complex, and there is, in fact, a lively scientific debate in progress about the relationship between human-caused climate change (especially in the Arctic) and the increased frequency of extreme cold-weather events across the United States blizzards, bomb cyclones, and the dreaded wintry mix.
