assuming u need to find the impedance looking into R10, the impedance is ((R13 + 1/(s*C6)) || (1/s*C5)) which inturn is in series with R12 (so add to it) and the combination in parallel with (1/s*C4). The resultant is in series with R11, and then parallel to (1/s*C3) and finally in series with R10.