In addition, he was a guest researcher at various universities and institutions, i.a. at Brookhaven National Laboratory (USA), Risø National Laboratory (Denmark), University of Kyoto, National Institute of Science and Technology, Gaithersburg-Washington, KTH Stockholm, and Uppsala University (Sweden). He was also member and chairperson of various scientific committees and advisory bodies, including those at the Paul Scherrer Institute in Switzerland, the Institut Laue-Langevin (Grenoble, France), Argonne National Laboratory, and the Helmholtz Center Berlin. In 1996 he was elected a Fellow of the American Physical Society, in 2001 he received an honorary doctorate from the KTH in Stockholm,

In addition to his scientific work at the University of Illinois and the Ruhr University Bochum with over 500 publications in peer-reviewed scientific journals on the structure, dynamics, magnetism and superconductivity of solids, he was supervisor and co-supervisor of more than 50 doctoral students in Urbana, Bochum and Mainz, organizer and co -organizer of numerous international workshops and conferences, editor and co-editor of five books, and guest lecturer at many summer schools in Europe. i.a. he was a guest lecturer in the European Graduate School "HERCULES" in Grenoble for the last 30 years, lecturing on the topic of scattering experiments with synchrotron radiation and neutrons.

At the beginning of 2000, the medical department at the Ruhr University Bochum developed a new study concept based on the model of the University Hospital Charité in Berlin: problem-oriented learning (POL). As a representative of the physics department, Hartmut Zabel was involved in the curriculum development. In addition to the standard physics course for medical students, he also supervised the physics-related seminars in the POL teaching format. Finally, he developed a new lecture series on "Medical Physics" for physics students and initiated a master course "Medical Physics" at the Ruhr University Bochum, which was later established and certified.