Interesting game! Definitely one of the more unique ideas I've seen so far, so huge points for that. Killing zombies using a pong ball is hilariously fun and that gave this small game a fair bit of replay value.
The game was probably a bit too hard imo. There are too many zombies to really run from and you get surrounded as soon as you make one wrong move. At some point there are just too many zombies to possibly deal with, and worse, the ball sometimes flies away too fast to follow off-screen and doesn't 'respawn' since it's still bouncing somewhere, leaving the player completely defenseless as they get surrounded. Makes the player feel a bit helpless as soon as the ball leaves the screen. When the ball stays in the right place and you keep bouncing it against the zombies over and over though, that is really fun!
Those polishes aside, this game is a great idea that could totally be expanded upon too. Would love to see some crazy powerups appearing on the field at some point, like multiple pong balls and stuff. A very replayable arcade game could come from this for sure!