No, not a zero sum game because of two reasons.
1. Trading reduces the probability of famines, because if some people think food will be in short supply, then they will store it and sell it later for a higher price. Making cash money and avoiding famine.
2. It provides credit to companies to grow and advance technology. Check out "the ascent of money" and how the medici family carried society in the 15th century.
However, the financial system could be improved, but don't want to rant about that because don't want to be annoying.
Finally, it feels like zero sum when I'm losing!