Night vision (infrared) is always black and white with cameras with the black being a bit less black than in daytime. It is perfectly normal. If you have bright outside lights you can most of the time just turn off the night vision and get good color video even at night. I have never tried to zoom during playback but if you get some video editing software you can cut individual frames from the video and blow them up as much as you want.
The foggy look is probable do to lack of auto focus, check your settings. Also the greater the zoom at night less sharp the focus. You will not be able to zoom in are out during playback mode because the recording is already complete.
Mine is ok at night because any motion that triggered the recording feature also triggered my motion light in the area of camera focus. I have mine set to the ultimate focus for the area it covers,but I don't believe you can alter the focus once it has been recorded.