I had no compilation errors. The zip file has always been created. I also could run the application locally.
I tried to delete the client folder as it helped me in the past: Cannot find module 'rxjs-compat/BehaviorSubject' - #4 by korchev
Now, I got compiler errors, which I haven't before. (couldn't find material.css in the assets)
Starting the deployment once more, seems to fix it. I will post if this solved the issue...