MuPAD cannot solve simple integration

I need to solve this integral:

 int(exp(-(t-z))*exp(-(z-mu)^2), z=0..t)

MuPAD cannot solve this, it returns the unevaluated integral. However, if I do the exponential multiplication myself and add the terms in the exponents, it can solve the integral:

 int(exp(-(t-z)-(z-mu)^2), z=0..t)

What's going on here? Why can't Matlab solve the first integral which is the same as the second one?