Yea they need a good trainer ASAP. This is way too much for you to try handling as a walker.
The fact that they can't be separated without possible injury PLUS the over the top behavior before the walk even starts means the owners need to be on board and put some heavy work in before expecting someone else to get the dogs to be responsive to them.
I hate stories like this. They just sound like normal mals who haven't gotten the training and structure they need, let alone exercise and mental stimulation.