As Mick says, push on the tabs marked on your original photo, they can be a bit tight so push the plug firmly back together before you press the tab and then pull apart.
Removing the tethered half from the radiator shroud can also be pretty tough, I put my hand up the back of the shroud and squeezed the barbs together which I found easier but just be carefull not to bend any rad fins with your knuckles. I've seen videos of people just pulling those connectors out but I found that a bit savage.