Alright, so I know this is fairly late, but I stumbled on this question and figured I'd might as well answer it.

So for a bit of background, in the aftermath of the Napoleonic war Prussia was propelled onto the world stage, it had been a fairly powerful regional power dating back to the reign of Frederick William I (also known as the "Great Elector"), who was responsible for laying the foundation of the Prussian Army and helping to build Brandenburg-Prussia into a formidable military and diplomatic force. But, Prussia had always been viewed as a "lesser" German power, behind the traditional ruler of Germany, Austria. Prussia was a member of the Holy Roman Empire, the ruler of the Empire was in theory "elected", but in reality the Austrian ruling dynasty the Hapsburgs held total control. The end of the Napoleonic wars saw Prussia gain a large amount of valuable territory, and it was the destruction of the Holy Roman Empire. Prussia had played a major role in the defeat of Napoleon, and it was now seen as one of the great powers.

Prussia wanted to become the most powerful German state, and one that could exert influence over all of Germany. To do this the Prussians needed to go through the traditional leader of Germany, Austria. They began fighting for influence over the other minor German states, of which there were many. The Prussians wanted a united German confederation with strong, centralized power in which Prussia and Austria would be the key players. the Austrians wanted a looser body that had really very little power. The Austrians won out, and the German confederation was born; the confederation was a very loose arrangement of the various German states. With Prussia's plans for a strong German confederation dashed, Prussia began to focus on two policies to bring the German states into the Prussian sphere of influence. One was through a federal security policy and through a customs union.

Various German states began to form custom unions, for example the states of Bavaria and Wurrtemburg formed a customs union. In 1827 a small German state called Hesse-Darmstadt asked if Prussia wanted to form a customs union, and Prussia agreed. From there the customs union kinda ballooned outwards and other small German states began to join, some states joined willingly, others required persuasion in the form of threats against their trade. Austria reacted with fear, as they worried Prussia's custom union could eventually grow to incorporate the vast majority of Germany. And those fears proved to be well founded, because Prussia's custom union came to incorporate many states in North Germany. The German customs union (the Zollverein) came into effect on January 1st, 1834. It was a union of the Prussian and Bavarian customs unions. Around 90% of all Germans now lived in state under the control of the Prussian customs union. Only Austria and a few very small states managed to stay out of the union.

Prussia's motives in creating the Zollverein were clear, they wanted economic domination over the German states and Prussia figured that if they could exercise economic control over the German states, that they could also exercise political control. The customs union did succeed in tying the various German states to Prussia economically, but as we would later find out in the Austro-Prussian war of 1866, didn't always lead to political control. Both sides (Austria and Prussia) overestimated the effect that the customs union would have, and when the two sides came to blows, most of the German states sided with Austria and not Prussia. There was also economic motivations, but they were secondary. And even so, the customs union didn't really lead to any substantial growth in the Prussian economy, so it failed in that respect as well.

There was some positives to the Zollverein, for one it established Prussia as a leading German state that the others could look to for guidance and leadership; and secondly it helped Prussia further distance itself from Austria and shown that the future of Germany did not have to be tied directly to Austria. Overall the Zollverein wasn't a major victory Prussia, especially considering its often viewed as such, but it did have some positives and can be looked at as a somewhat important moment in Prussia's unification of Germany.

Sources:

Iron Kingdom by Christopher Clark

The Long Nineteenth Century: A History of Germany: 1780-1918 by David Blackbourn