The pro agility drill can be improved by simply practicing it. Here are some tips: When moving from line to line angle in to the line and push off the inside part of your foot. As you push off immediately cross over keeping the foot low to the ground to minimize air time.
The second thing you can do is to become excellent at absorbing force. Doing eccentrics and isometrics in the weight room is good for force absorption as well as jumps, particularly box jumps.
Thirdly, the ability to overcome your bodyweight and redirect force is the key to quickness. Losing unwanted body fat through disciplined eating is key to becoming a quicker athlete.
Lastly, remember that the pro agility drill is just a measure of agility but there are some interesting studies on reactive agility being more important. One study looked at 1st team rugby players and 2nd team rugby players. Oddly enough the 2nd team rugby players were faster athletes on close agility tests like the pro agility tests. The difference between the 1st team and the 2nd team was the ability to make decisions under pressure (reactive agility) so I want to encourage you to choose agility exercises that involved a decision making component and get some friends to take part in the fun. You will be a better athlete because of it.