how can ekko beat Heimerdinger

Throw out your long range Q to break his turrets. Don't just dive onto him willy nilly, that's asking to get an easy stun and lazers flying at you from everywhere. If he has only 1 turret up I say you can go for a trade but anything more and you need to think about how much damage you're gonna be taking.

You CAN stun his turrets so if he is just playing really close to his turrets try to land parallel convergence near turrets and on him. Or you can just use the shield for a trade normally. If you manage to destroy his turrets and get him to his tower you can harass him with parallel convergence dives and quick trades. Just be wary of his stun and try your best to dodge his W and E. If you dodge those abilities his turrets wont charge up lazer.

Always be ready to chronoshift out because new donger has a lot more burst over sustained damage now. Don't underestimate his turrets.