What is 'Z.Z. Anflug' and 'ZZ Landung'?

[Tim O.]

Hi all

I am plodding through the translation of a set of Flugbuch from 1937-1943 for a Luftwaffe Radio Operator. Thankfully his writing is beautifully clear but I just wanted to check an abbreviation. He mentions 'Z.Z. Anflug' while in training and 'ZZ Landung (Brennstoffmangel)' i.e. due to fuel shortage, after a mission in Norway. At this time in his career all flights were in the Ju52/3m.

Any clarification on ZZ in these two contexts would be much appreciated.

Best wishes
Tim O.