From 2 friends to 13,000 ZSers: Celebrating 40 years of passion and impact

Before it was a global consulting firm, ZS began with Andy Zoltners and Prabha Sinha, two friends who shared a love for solving complex problems. Andy and Prabha met in 1973 at the University of Massachusetts, where they collaborated on a multiple-choice knapsack algorithm to plan meals for the U.S. military. The project quickly gained attention from organizations looking for innovative resource allocation solutions.

After earning their doctorates, Andy and Prabha became professors at Northwestern University. Outside of class, they began using the world’s first personal computer-aided territory-mapping system to design sales force alignment models. Their research turned into a small side business—ZS (Zoltners and Sinha)—which eventually grew into what it is today: a firm with more than 35 offices worldwide and 13,000+ ZSers using their passion and expertise to transform global healthcare.

In the early days, before ZS was officially founded, Andy and Prabha spent much of their time knocking on doors and calling friends to pitch their nascent ideas.

“At that time, Andy was trying everything—from territory alignment and sales force sizing to zero-base budgeting and catalog space planning,” Prabha recalls, laughing at the memory of those early uncertainties and rejections.

Then in 1977, Andy got a call from a former classmate working at a top 10 pharmaceutical company’s internal consulting arm. That meeting led to a breakthrough: using the multiple-choice knapsack algorithm to size a sales force—an idea that would become central to ZS’s founding.

The two made a bold bet on their vision. Prabha took a six-month sabbatical from teaching and rented out his house to pursue several ventures, including one that ultimately fell through. Then Andy called with good news: a contract with Wrigley, the chewing gum company. That early win was a turning point.

The big break came in 1982 at a Pharmaceutical Management Science Association (PMSA) meeting. Andy gave a live demonstration on an Apple computer. Three pharmaceutical companies signed on, and one invited them to present to affiliates across Europe.

“After multiple successful projects in Europe, the VP of marketing asked Andy a question,” Prabha says. “I don’t remember what it was, but I’ll always remember Andy’s response: ‘I don’t know.’ That honesty with clients—that authenticity—was true then, and it’s still true today.”

Authenticity has anchored ZS since it was founded in 1983. Clients trust us to be excellent and effective—but also humble and honest. Above all, we live by the values Andy and Prabha instilled: treat people right, get it right and do the right thing.

As ZS’s client work grew, Andy and Prabha continuously improved the territory alignment algorithm and software based on client questions. This client-driven, technology-enabled mindset continues to define ZS today. We work side by side with clients to solve complex challenges in innovative ways.

As the business expanded, Andy and Prabha began hiring talent to grow ZS—and grow with ZS. Back then, teams were much smaller, and most new work came through word of mouth and quality delivery.

“One of the key things we learned over the years is that hiring isn’t about cloning ourselves,” Prabha says. “We look for people who bring new skills, expertise and perspectives.”

That mindset fuels the diverse talent at ZS. By prioritizing inclusion and belonging, ZS attracts the broad range of experiences necessary to help clients solve the problems that matter most.

“The company was flying,” Prabha recalls. “We were expanding geographically—first to London, then to New Jersey, and beyond. Then we expanded practice areas and industries. That growth and customer success brought new challenges—and required a lot of hard work and creative thinking.”

Forty years later, ZS has grown far beyond its original focus. Today, we serve clients in global healthcare, technology, agribusiness and food, high-tech, travel and transportation and more. We help them optimize clinical trials, bring new products to market and improve business operations. And behind every solution, we remember: there are real people whose lives depend on access to affordable medicine, quality diagnostics, financial stability, food security and healthy living conditions.

Though much has changed, our values remain the same. ZS continues to lead with integrity, invest in its culture, and collaborate deeply across teams. We still use our passion—just like Andy and Prabha did—to change lives.

“My expectation is that every generation will leave a stronger ZS to the next,” Prabha says.

Before passing away in 2023, Andy shared his vision:

“I hope for a ZS that takes care of its people, takes care of its customers, innovates and builds expertise.”

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