I wouldn't include a "since" term in a conditional diagram. However, I would be able to represent "none of Y is Z."
Y - - - -> not Z Z - - - -> not Y Let's call this a rule.
If I understand what you mean by "Since X," you are saying that the rule above exists as a result of X. However, "Since X" implies to me that X already exists. It is not conditional, so there is no need to put it in your diagram.
Are you referring to "since wealth is the basis of political power?" This is not something that I would diagram. This has simply set money = political power. I would just do the following:
