A CONTRACT CLEANING COMPANY THAT TRULY MAKES A DIFFERENCE. Greenzest is a commercial cleaning company that puts the greatest priority on the welfare of the planet, our people and our partnerships. As one of the country’s leading office and commercial cleaning contractors, we set out not to appear different, but to actually make a difference. Our business is founded on a Corporate Sustainability model that sits firmly at the heart of everything we do and is central to all of our policies, strategy and operational procedures.