The US Dollar is definitely a major (in fact, it is THE most traded and most used for reserve purposes), but the Polish Zloty is not, therefore the pair the two make is not a major pair either. The USD/PLN is not a commodity pair.
The USD is the national currency of the United States, but interestingly, its major reserve currency status means that more of it is held outside the country than within. No fewer than 7 other countries use the USD as their national currency, among them Ecuador, El Salvador and Panama.
The USD permeates the global economy to an unprecedented degree. Some commodities – like Gold and Oil- are only traded in USD, and the value of just about everything is best expressed in USD too. Some 23 countries have their currencies pegged to the USD.
The value of the USD is controlled by the Federal Reserve.
The history of the Polish Zloty is a rather eventful one. Introduced and re-introduced no fewer than 4 times, the latest incarnation of the currency finally seems to have broken the curse that affected some of its predecessors. Economic growth has been steady for the country, and the Zloty has reflected this well.
Unfortunately, Poland is compelled by treaty to eventually adopt the EUR as an EU member. This means the Zloty will be phased out, though exactly when this will happen is unclear. According to the Polish authorities, the introduction of the EUR will only happen when the economic interests of the country call for it.
The USD/PLN pair is closely correlated with the EUR/USD one, given Poland’s close links to the EU and to the Eurozone. The political situation in the country as well as the rate of economic growth, do indeed create some trading opportunities every now and then.