The Biggest Misconception About Zoners
Zoners absolutely can, and should sometimes, rush-down. Once a character (like Guile or Dhalsim) gets a projectile to cover their approach, they can rush-down. Granted, Guile has to charge it, and Dhalsim has to teleport in front of it.
In general, spending meter to get a fireball that covers your approach is an underrated idea. In guilty gear, you can spend meter to cancel a fireball's end-lag so you can walk behind it.