The phrase "achieved mainly" is correct and usable in written English.
It can be used to indicate that something was accomplished primarily or predominantly through certain means or methods.
Example: "The project's success was achieved mainly through effective teamwork and communication."
Alternatives: "primarily accomplished" or "largely attained".
Greater emphasis on the achievement of scale economies: scale economies were achieved mainly by closing less performing plants and expanding the production capacity of the remaining ones.
However, this would have been worse if not for a £65m cost-cutting push achieved "mainly as a result of significant programme cost savings".
This was achieved mainly by bringing together a number of waste and recycling contracts into a single one with tight sustainability focused specifications.
But the victories were achieved mainly by the fleet, which was manned by the poorer Athenians, who were less well disposed toward Sparta.
With the great development of coal mining in Henan, attention has been focused on silicosis prevention, which is being achieved mainly by improving working conditions.
The British victory had been achieved mainly because India's superior resources had made possible a sustained campaign running through two rainy seasons.
Since 1990, the opening up of archives in the former Soviet bloc has enabled real breakthroughs in research on the Holocaust and on Nazi rule in eastern Europe, achieved mainly through the work of younger German historians.
The return to profitability has been achieved mainly because of "significant slowing" in impairments in the wholesale business, which has been the cause of much of the criticism levelled at Lloyds management since the HBOS deal.
However, 63.87% of norfloxacin maximum removal efficiency was achieved mainly by sorption.
In each of these cases, this engineering was achieved mainly by modulating expression of native genes.
An energy-efficient design can be achieved mainly through accurate design of built –environment forms.
