Still not getting ZoCs

[76mm]

I thought that I had ZoCs figured out in this game, but something happened in a current game that shows that I don't. Could someone explain what is going on?

at the start of my opponent's turn, my cav unit had an enemy thureo unit it its primary ZoC. None of my other units had it in its primary ZoC. My unit highlighted in blue, enemy unit in red:

2020-09-23 (2).png (583.31 KiB) Viewed 844 times

2020-09-23 (2).png (583.31 KiB) Viewed 844 times

Then during my opponent's turn he was able to turn his unit's facing (his unit in blue):

2020-09-23 (2).png (583.31 KiB) Viewed 844 times

2020-09-23 (2).png (583.31 KiB) Viewed 844 times

Dammit, I can't get the screenshots to attach properly...see the last picture below for the end-turn situation.

Can someone explain what I'm missing? Thanks.

[melm]

If a unit's flank is threaten, in your case the superior warband threatening the thureophoroi's, it can turn 45 degree.

[76mm]

Aha, missed that slight detail! Thanks much!