The phrase "complement and strengthen" is correct and usable in written English.
You can use it when you want to show that something is making another thing better or more powerful. For example, "The addition of new equipment to our laboratory will complement and strengthen our research capabilities."
This will complement and strengthen the traditional attributes of the bookshops to which the company remains fundamentally committed".
But we see a ban treaty as something not to replace the NPT, but as something to complement and strengthen it, like the comprehensive test ban treaty did in the 1990s".
Proactive tools and approaches can help complement and strengthen current security solutions.
Elemental mapping techniques can complement and strengthen data collected with sensors.
Marketers and agencies struggle to understand how their efforts across different channels complement and strengthen each other.
The science and technology partnerships and initiatives help to complement and strengthen collaboration among the partners, within their respective mandates and expertise.
The official role of chaplain is complemented and strengthened by the unofficial role of a Christian who happens to hold the rank of private.
Ongoing efforts carried out with UNESCO, USAID and the World Bank will be complemented and strengthened.
Existing programmes, including those carried out with the United Nations Educational, Scientific and Cultural Organization (UNESCO), the United States Agency for International Development USAIDD) and the World Bank, will be complemented and strengthened.
Our findings will be complemented and strengthened by pilot projects that are currently underway across some agencies to standardize wait list definitions.
Thus, this initiative will complement current initiatives and strengthen European public health at large.
