ZA means to sit. ZEN means dhyana, Zen, meditation. ZAZEN means sitting-dhyana, sitting-zen, sitting-meditation.
To leave ZAZEN untranslated, in English phrases such as "sit in Zazen" or "practise Zazen," was my mistake.
When, in translating Shobogenzo into English, I had the opportunity to demistify the Buddha's teaching, I failed to hit the target. It was my mistake.
ZAZEN means sitting-dhyana, sitting-zen.