Complex sentence: During that time he held many exhibitions at the Kunsthalle and also in other museums in the area, such as the Kunsthaus of Zurich, Ecole Polytechnique, Federal of Zurich, and the Cabinet of Prints, of Geneva.
Split into simpler sentences: During that time he held many exhibitions at the Kunsthalle and also in other museums in the area. There were many museums interested in his work, such as the Kunsthaus of Zurich, Ecole Polytechnique, Federal of Zurich, and the Cabinet of Prints, of Geneva.