If player1 can make the same widget with less resources than player2, its not zero-sum. That does often entail that player1 has some advantage, which could be any number of things. Is that OK?
It happens because the less wealthy player has a lot more to loose then gain in an unequal economy. That is even if a trade outcome is favorable to the less wealthy player, it is unlikely that the outcome is significant enough to change the balance. However it is much more likely if an outcome is unfavorable that it will significantly hinder any future opportunities for the poorer player.
On the other hand, a loss for the wealthier player is unlikely to significantly effect future outcomes for them. The only likely way for a wealthy player to have a significant loss if they land a devastatingly bad deal with another equally or more wealthy player. The chances of that happening at random is pretty low overall, and gets lower the wealthier you are.
If player1 can make the same widget with less resources than player2, its not zero-sum. That does often entail that player1 has some advantage, which could be any number of things. Is that OK?