I would tackle the PPL exams before going too deep.
By the time you have finished them it will just be a case of building on what you covered during your PPL studys for your ATPL.
I'm going to get shot down here but my first ATPL subjects are Principles of flight, Performance, Powerplant, Electrics and Airframes and systems and I have only seen basic maths so far etc No hardcore math at all....
I was led to believe that ATPL was a maths and physics trial more that anything else. I have found that as its all related to what you are working towards it all falls into place as you go
