NO this is not possible....the 58PZ700U does not have removable speaker like the 5080HD. Thats what makes the pioneer able to hook up other speakers if desired. It should be noted that it does only put out 17 watts, so its not really enough to drive anything nice. Any particular reason you are looking for them to be removable?
My friend has a Pioneer 5080 and is able to connect external speakers directly to his plasma without a receiver....
Is it possible to connect external speakers to the Pani without using a receiver??
No, the Pioneer has regular speaker wire connectors on the back but the Panasonic consumer models do not have such speaker connections. You'd have to either use the built-in speakers, or turn them off in the menu and route the audio to an A/V receiver instead.
However the speakers and audio quality on the PZ700U (and it's replacement PZ800U) is very good - probably better than any flat panel TV on the market. 2 main speakers + 2 woofers and a total of 31 watts of power.