Depress the latch with your thumb & pull?  I don't recall it being any different (or any more difficult) from any other latching connector in the car.

Thanks. That's what I've been doing, but they're a real pain to separate, or at least trying to separate the connectors in the engine compartment is. I wonder if a type of grease on the seal may make it easier. Has anyone you ever seen any of those latches break off (does that type of plastic age)?

These are the originals.
I hadn't thought about other makes.