How to create a measure from two different tables?

Please see my scenario below.

I have three tables. One a Dimension Table and two other fact tables. I have one measure in each of the Fact Tables and they join to the dimension by a key. Now I want to create a 3rd measure which is nothing but New Measure = DIVIDE([Count from Fact table 1], [Count from Fact table2], 0).

How to acheive this? Any ideas will be helpful.