Hitchcock and Partner is a US tax advisory firm based out of Zürich, Switzerland. Mainfort Steuerberatungs & Rechtsanwaltsgesellschaft mbH is a German tax advisory firm based out of Frankfurt, Germany.
The two companies work together as a Joint Venture to service clients needing assistance with both US and German tax advisory services. The "Joint venture" operates under the name US European International Tax, or "USEIT" for short.