water line coupling disconnect trouble
 

2005 Rendezvous. 3400 SFI engine.
The metal waterline comes off the top of the water pump, across the front of the engine, around the right side of the engine. It couples with a flexible hose in the rear of the engine compartment.

I cannot get the connection of these two hoses apart. There are press-tabs or squeeze-tabs top and underside of the coupling. They appear to be compressing when I squeeze them, but I cannot get it apart.
All other disconnections have been made.

Any suggestion are welcomed. Thank you.