Solving three impedances in series
Let's translate your words into an equation for the equivalent impedance.


  Since C1 and R1 are in parallel


$$Z_1 = R_1||\frac{1}{sC_1}$$


  likewise C2 and R2


$$Z_2 = R_2||\frac{1}{sC_2}$$


  Solving three impedances in series


$$Z_E = Z_1 + Z_2 + R_3$$