Our team currently has (2) Marketo instances and (1) GoTo Webinar account. Can this GTW account be connected to both Marketo instances?
Yes technically you should be able to connect the GTW account to both Marketo instances. I believe the setup steps would remain the same.
The question that I would pose is how would you differentiate the campaigns that you are running for one Marketo instance versus another? That would be a question for GTW.