@Christian Wolinski 

Thanks for your answer. I inputted everything with "Maple Math" - that the interface turns it into tiny .gifs-files is not something that I was aware of. Here is the direct input from Maple:

total := (((((D^2/(alpha^2*mu^2) + D^2*exp(2*(-t + t1)*alpha*mu)/(alpha^2*mu^2)) + D^2*exp(2*(-t + t1)*alpha*mu)/(alpha^2*mu^2)) + D1*D/((alpha*mu*tau0 + 1)*alpha^2*mu^2) - (-alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 + 1)/tau0) + exp(2*(-t + t1)*alpha*mu))*D*D1/(mu^2*alpha^2*(alpha^2*mu^2*tau0^2 - 1)) + (alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 + 1)/tau0) - exp(2*(-t + t1)*alpha*mu))*D1*D/(alpha^2*mu^2*(alpha^2*mu^2*tau0^2 - 1))) - (-alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 + 1)/tau0) + exp(2*(-t + t1)*alpha*mu))*D*D1/(mu^2*alpha^2*(alpha^2*mu^2*tau0^2 - 1))) + (alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 + 1)/tau0) - exp(2*(-t + t1)*alpha*mu))*D1*D/(alpha^2*mu^2*(alpha^2*mu^2*tau0^2 - 1)) + D1*D/((alpha*mu*tau0 + 1)*alpha^2*mu^2) + D1^2/((alpha*mu*tau0 + 1)^2*alpha^2*mu^2) - (alpha*mu*tau0*exp(-(-t + t1)*(alpha*mu*tau0 - 1)/tau0) + alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 - 1)/tau0) - alpha^2*mu^2*tau0^2 - 1)*D1^2/(alpha^2*mu^2*(alpha^4*mu^4*tau0^4 - 2*alpha^2*mu^2*tau0^2 + 1))) - (alpha*mu*tau0*exp(-(-t + t1)*(alpha*mu*tau0 - 1)/tau0) + alpha*mu*tau0*exp((-t + t1)*(alpha*mu*tau0 - 1)/tau0) - alpha^2*mu^2*tau0^2 - 1)*D1^2/(alpha^2*mu^2*(alpha^4*mu^4*tau0^4 - 2*alpha^2*mu^2*tau0^2 + 1))

D1^2/((alpha*mu*tau0 + 1)^2*alpha^2*mu^2) + 2*D1*D/((alpha*mu*tau0 + 1)*alpha^2*mu^2) + D^2/(alpha^2*mu^2)

r2r2 := %;
 

total - r2r2;