With dual WAN connectivity where each serves different purposes, you want to start with setting up proper routing. You need to make sure all MPLS and VoIP traffic is going through your T1 while the Internet traffic is going through the Cable. Using static routes, manually create specific routes to go through the T1 and set default gateway to go through the Cable.
In regards of port forwarding with ZBF in place, I never really like the approach since I think ZBF is not mature enough compared to firewall inspection on ASA. You may want to play around with ZBF setting to have successful result (which I never had