When Toph Beifong discovered Metal Bending in Avatar The Last Airbender (ATLA) she also opened up new possibilities to for the citizens of her native Earth Kingdom. In Avatar the Last Airbender the Earth Kingdom was portrayed as one of the world's backward regions (Probably behind the Southern Water Tribe). Many of its citizens were languishing in poverty as a result of the 100 year war. Many families in the Earth Kingdom were separated by incarceration,death or both. Many of its citizens were running to Ba Sing Se for safety and by the end of the second season of Avatar The Last Airbender, Ba Sing Se fell to the forces of the Fire Nation.
The Legend of Korra, a sequel to ATLA explored the avatar world 70 years after the events of the 100 year war. Republic City was introduced and in many ways its showed how the people of that world moved forward after the war. There were intermarriages, inventions, innovations, industrialization e.t.c. The third season of Legend of Korra introduced us to both Zaofu and modern Ba Sing Se. If we were to compare which city was more modern Zaofu wins hands down. Ba Sing Se still had its walls that splits its 3 classes of citizens intact. The Dai Li (Earth Kingdom's Secret Police) were very much in operation. Zaofu on the other hand is in pristine condition and everyone is encouraged to strive for his/her personal best.
Zaofu can be comparable to the modern Republic City in many ways. The only difference is that Zaofu is more homogeneous (most of its citizens are of Earth Kingdom heritage). In fact Zaofu easily surpasses Republic City is some aspects such as security, organization and technology (the Zaofu rail network is the best i saw in the series). If you ask me Kuvira (the badass book 4 villain) was able to succeed in her conquest of the Earth Kingdom/Earth Empire because of the talent from Zaofu. The fact that after the fall of the Earth Kingdom as a result of Zaheer and his badass crew the world leaders went to Zaofu for help speaks volumes.
****SPOILER ALERT FOR THOSE WHO HAVE NOT WATCHED THE FINALE****
So how does Toph's discovery of Metal bending have to do with the success of Zaofu? I have already stated the answer. Zaofu is the home of the Metal clan which was founded by Suyin Beifong (Toph's cool daughter). Suyin showed great despise for the monarchy and now after Prince Wu decided to abdicate the throne the model of Zaofu may be applied to the rest of the Earth Kingdom. Metalbending may be a requirement for you to be considered a master in Earthbending (another option being lavabending). The technological innovations and inventions bred in Zaofu are well placed to assist the new Earth Nation (since its not a kingdom anymore) and possibly the world.
In ATLA, the Fire Nation was an industrial superpower but going forward i expect the the Earth Nation led by Zaofu to be the new leaders of that world's industry.