Not sure how it works but they’ve been doing it in Cricket (At least that’s what I was told) for a while now.
Perhaps a thermal camera of some kind?
The vertical parameters of the zone should be based off of proportions of the batter, per the rules. I have no idea about cricket, I know they are standing in front of sticks and a pitched ball bounces before they swing. Do they have a strike zone?
The only way I can imagine it is if there are sensors in the uniform somehow. You need a way to get strike zone changes per size of player as adjusted by batting stance. At least per the rules.
FReegards