Some RICs do not seem to exist for some rates (if I am not mistaken) e.g.: TWDZMK

All these RICs are invalid: TWDZMK=, ZMKTWD=, TWDZMK=R, ZMKTWD=R so I guess we must triangulate this rate using USD but then if you got an update for only one of the currencies then you would need to recalculate the rate which could then be inaccurate

Is there a set way to calculate FX rates using Reuters or obtain every possible rate?