Hello Rockdog and welcome to the forum!
The Y-cable connectors have two "noses" while the the transducer connector has two "gaps" where the noses fit in. I suggest you take a hair dryer and gently heat up the connector to give the plastic a bit more flexibility to let the noses slip out of the gaps.
Whatever you do: Do NOT pull on the cables, no matter how tempted you are to get a better grip.
Hope this helps!
Regards / Harry