I am trying to get a managed package (Zuora) to use the latest Exchange rate in my org, we use dated exchange rates and we use 3 rates and need it to at least use the latest exchange rate. Is it possible and if so, how?
Unfortunately Salesforce only supports dated exchange rates natively within the context of opportunities. I don't know anything about Zuora but my guess is that their solution is built on custom objects which are not supported by dated exchange rates. There is an idea that addresses this issue but it doesn't look like it will be supported anytime soon.
I had a similar issue on a project I worked on recently. Fortunately for us, this was a custom application we built and I was able to access the dated exchange rates via Apex which we then applied to our custom object records. Since you are dealing with a managed package, you would have to work with the vendor to see if they can enhance their application to support multi-currency with dated exchange rates (or somehow extend their application and do this yourself). Here is a post from a developer at FinancialForce that discusses this issue and how they had to essentially build their own currency conversion system from the ground up to support advanced currency management.