Question: How do I invlaplace so complicated expression?

I want to invlaplace the following complex expression that I call PQ.

>PQ:=(cosh((1/2)*eta*sqrt(C3^2+4*C1*s))*sqrt(C3^2+4*C1*s)+sinh((1/2)*eta*sqrt(C3^2+4*C1*s))*C3)*(cosh((1/2)*eta*C3)-sinh((1/2)*eta*C3))*(-cosh(C4)-sinh(C4)+s)/(s^2*(-sinh((1/2)*C3)+cosh((1/2)*C3))*(sinh((1/2)*sqrt(C3^2+4*C1*s))*C3+sqrt(C3^2+4*C1*s)*cosh((1/2)*sqrt(C3^2+4*C1*s))))

where C1 C3 C4 eta are constant .

Then I do like this

>invlaplace(PQ)

But I got

invlaplace((cosh((1/2)*eta*sqrt(C3^2+4*C1*s))*sqrt(C3^2+4*C1*s)+sinh((1/2)*eta*sqrt(C3^2+4*C1*s))*C3)*(cosh((1/2)*eta*C3)-sinh((1/2)*eta*C3))*(-cosh(C4)-sinh(C4)+s)/(s^2*(-sinh((1/2)*C3)+cosh((1/2)*C3))*(sinh((1/2)*sqrt(C3^2+4*C1*s))*C3+sqrt(C3^2+4*C1*s)*cosh((1/2)*sqrt(C3^2+4*C1*s)))))

Nothing done!

How to do this ? PLZ help me in any way as you can,thank you.

I am very interested in getting it.