Considering the fall feasts and how the Most High has historically done amazing works on all of the appointed feasts, I would lean towards the Fall, in particular aligning with either the feast of Trumpets (announcing the birth of the saviour) or the feast of Booths/Tabernacles ("he came and dwelt/tabernacled among us"). Good point on Zechariah's service as well.
Considering the fall feasts and how the Most High has historically done amazing works on all of the appointed feasts, I would lean towards the Fall, in particular aligning with either the feast of Trumpets (announcing the birth of the saviour) or the feast of Booths/Tabernacles ("he came and dwelt/tabernacled among us"). Good point on Zechariah's service as well.