Complex sentence: He then became a professor at the Enrico Fermi Institute in Chicago from 1956 to 1963, when he moved to the University of Oxford as a Royal Society research professor, although keeping a connection with Chicago until 1966.
Split into simpler sentences: He then became a professor at the Enrico Fermi Institute in Chicago from 1956 to 1963. Next, he moved to the University of Oxford as a Royal Society research professor, although keeping a connection with Chicago until 1966.