Professor Zajac’s research, teaching, and consulting focuses on strategic management issues. His award-winning research on strategic alliances, corporate governance, and strategic adaptation has been published widely in major academic journals, such as the Strategic Management Journal, Administrative Science Quarterly, Organization Science, Academy of Management Journal, American Sociological Review, and Management Science. Professor Zajac is Co-Editor of the Strategic Management Journal, and an editorial board member of the Asia Pacific Journal of Management. He has chaired the International Strategic Management Society Conference and the Business Policy and Strategy Division of the Academy of Management.

Professor Zajac has developed several popular courses at Kellogg in his areas of expertise: Creating and Managing Strategic Alliances addresses the design and management of strategic alliances such as joint ventures, licensing agreements, consortia, and other forms of cooperative strategies. Advanced Strategic Management examines how organizations can more effectively adapt to changing environments (with an emphasis on integrating strategy formulation and implementation challenges). Organizational Design examines the contribution that structure and systems can make in the implementation of an organization’s strategy. Corporate Governance analyzes the interdependent roles of the CEO, board of directors, shareholders and other stakeholders in the modern public corporation, both in the U.S. and abroad.

Professor Zajac has also created a highly successful executive education program on strategic alliances, and is active in executive education and consulting in North America, Europe, Asia, and Latin America in the areas of strategy formulation and implementation, strategic alliances, and corporate governance. He has worked with organizations such as Abbott, AstraZeneca, Aventis, Baxter, Blue Cross/Blue Shield (the Association, HCSC, and the Michigan, Minnesota, Illinois, and North Carolina plans), Brady, Bristol-Meyers Squibb, Brunswick, Cargill, Caterpillar, Chiron, Cigna, Commonwealth Edison, ConocoPhillips, Cooper Tire and Rubber, Dade Behring, R.R. Donnelly, Edwards Lifesciences, the FBI, FTI Ringtail, Gen-Probe, General Mills, W.W. Grainger, Harnischfeger, Hearst, Healthways, Hollister, IBM, the Institute for Corporate Directors (Canada), Johnson & Johnson, Land O’Lakes, Libbey, Eli Lilly, MARKEM, Merck, Monsanto, Moore, Novo Nordisk, Pfizer, Premier, Procter & Gamble, Public Service Company of New Mexico, Rockwell Automation, Rockwell Collins, Savoy Brands Internacional, Schering-Plough, Siemens, Topco, Toyota, the U.S. Customs Service, Vicinity, Zurich Insurance, numerous professional associations (particularly in health care), and a wide variety of other organizations. He served on the board of directors of Roberts Industries, and is currently a board member at PeopleFlo Manufacturing, Pioneer Surgical Technology, and The Wetlands Initiative.

Professor Zajac was recognized as one of the "most-cited researchers worldwide" in 2008 and 2009 in the Institute for Scientific Information's yearly list of the most highly cited researchers, which includes less than one-half of one percent of all published researchers.