Hi and thanks for your question!
It´s perfectly possible to control software on the computer with the Zaquencer, as long as the software can be triggered by Midi notes. For this you would hook up the Zaquencer to the computer with a standard Midi-USB interface, or sometimes this might be integrated in your Audio Interface.

I guess all VST instruments should be able to receive Midi notes and play them. While I haven´t personally used Reason, I´m quite sure it´s devices can also be controlled by incoming Midi notes, as it´s a pretty standard feature. Maybe some Reason users can weigh in here?