You can do this in playground. You can input the two sensors and set kind of like this. This virtual sensor outputs 1 degree C when CPU is above or equal to 75C or when GPU is equal or above 45C. Then I assign this to the software sensor with offset value of 50 so when the virtual is 1C then the software is 50C. Then I use this software sensor to ramp up pump speed when either of these two reach mentioned temperature points.
I would suggest to control fans using water temperature, its the best way to avoid needless fan ramps up and down.