/ / / 3 \ / 3 \\ \
| | 3*cosh|------| 6*sinh|------|| / / 3 \\|
| | / 3 \ \-1 + z/ \-1 + z/| | 3*sinh|------|||
| / 3 \ 3*|2*cosh|------| + -------------- + --------------| | / 3 \ \-1 + z/||
| 18*cosh|------| | \-1 + z/ 2 -1 + z | 9*|2*cosh|------| + --------------||
| / 3 \ \-1 + z/ \ (-1 + z) / \ \-1 + z/ -1 + z /|
3*|2*sinh|------| - --------------- - ---------------------------------------------------- + -----------------------------------|
\ \-1 + z/ -1 + z -1 + z -1 + z /
$$3 \left(2 \sinh{\left(\frac{3}{z - 1} \right)} + \frac{9 \left(2 \cosh{\left(\frac{3}{z - 1} \right)} + \frac{3 \sinh{\left(\frac{3}{z - 1} \right)}}{z - 1}\right)}{z - 1} - \frac{3 \left(2 \cosh{\left(\frac{3}{z - 1} \right)} + \frac{6 \sinh{\left(\frac{3}{z - 1} \right)}}{z - 1} + \frac{3 \cosh{\left(\frac{3}{z - 1} \right)}}{\left(z - 1\right)^{2}}\right)}{z - 1} - \frac{18 \cosh{\left(\frac{3}{z - 1} \right)}}{z - 1}\right)$$