When you look at the O2 connectors, there is one side with an automotive fastener/push pin holding the connector to something. On the opposite side of the fastener (think of fastener as bottom), or top, there is a very small black tab that when held in releases the actual O2 sensor plug locking tab, this is a very small tab at the top rear of the connector in a small cutout area, hard to find. You have to gently push the tab down, while pulling the connectors apart. It's a two hand procedure, as the tab must be held down the entire time.

The connectors will most likely be somewhat difficult to remove from each other, so instead of trying to push the tab even harder, gently hold the tab down and rock the connectors around inside of each other, then gently work them apart.

Be careful with the connectors, the "release tab" is usually on the chassis side of the wiring (the part that leads to the ECM), not generally on the device attached to it. If tabs get broken, you will have to hold the connectors together with a zip-tie.

Too late for pics outside tonight, see if I can take one in the morning.