If a race car completed a full lap and is where he started, why is his average velocity zero but his average speed isn’t?

Velocity is displacement over time, whereas speed is distance over time. Displacement is the shortest distance from point A to point B(a straight line). In this case, the starting point(point A) is the ending point(point B) therefore the distance between the start and finish is zero, and zero divided by the driver’s lap time is zero(from the equation), meaning zero velocity. Distance however is the total length of the track in this case. The average speed will be the length of the lap over the time taken to complete the lap, which would be larger than zero.