random blinking without delay and blinking with delay in 1

Projects Programming
12

It's nice when something works.
Now, can it be improved and/or tidied up even more ?

Having copied the value of millis() into the currentMillis variable at the start of loop() why not use it throughout the program when you need the value of millis() rather than reading it again ?

  led1zwtimer = millis () ;
  led2zwtimer = millis () ;
  led3ktimer = millis () ;
  led4_5ktimer = millis () ;
  led6krtimer = millis () ;

Numbered variables almost always means that arrays could be used to shorten code.

   digitalWrite( led6kr, digitalRead( led6kr) == HIGH ? LOW : HIGH);

digitalWrite(led6kr, !digitalRead(led6kr));

would be easier to read and understand