After 'Duck Soup,' Zeppo decided to leave the Marx Brothers' act to pursue other interests. He felt that his role as the straight man was limiting and that he had the skills and ambition to succeed in business.

Zeppo, along with his brother Gummo, founded the Marx Brothers Agency, a talent agency that represented several prominent actors, writers, and directors. This venture demonstrated Zeppo's business acumen and his ability to identify and nurture talent.

Zeppo displayed a keen interest in mechanics and engineering. He invented a wristwatch that monitored the pulse rate of heart patients and secured a patent for a self-centering clutch mechanism. These inventions showcased his innovative thinking and problem-solving skills.

During World War II, Zeppo's clutch mechanism proved valuable in military vehicles, particularly in tanks and airplanes. This contribution highlighted the practical applications of his inventions and their impact on national defense.

After the war, Zeppo continued to develop and refine his inventions. He also pursued other business opportunities, demonstrating a diversified entrepreneurial spirit.