low-flying disk with radical "Z" turnWitnessed a high-speed saucer flying through low cloud cover (about 1500 ft). Flying speed of shooting star. White glow around disk with small lights around edge of disk, blue red and white. Flew level to the ground, then sudenly did a lateral "Z" course change. left then right and disappeared instantly. The turns were 90 degrees and were instant with no slow down. There was no sound at all. This was witnessed by two people.