It's a Canon fact that Zack Paterson dosen't like candy but if he had a S/O he would always buy them there Favorite ones. MAYBE even try them.
I always imagined that his main Love languege is acts of Service and gift giving.
His gifts are meaningful (buys you your fav perfum/ flowers and more) but there also very practical, something that he knows you will use in the long run.
He's the typ of Partner who wants to make your life easier and is actively trying to make it easier for you so you will have less to worry.
If his S/O mentioned she likes something he will get it for them. Like I said his gifts are very sweet.
He dosen't expect gifts in return but anything you give him he will carry it with him or it is save at home and he will make sure to never ever lose it.
He values the time with you since he is a pretty bussy men (a double agent and police men).
Can't really see him being big on public affection, when your outside with him he won't kiss or hug you, the only kiss you recive in public is a hand kiss and most of the time when your walking you have your hand around his arm.
He is very reliable and trust worthy, any secrets you gave him he will take it to the grave.
He expects the same from you.
I can't really picture him talking a lot about the relationship, maybe here and there but nothing much.
He dosen't see the point in oversharing.
He's very patient and serious about you and wants to make this work.
The only ppl that know about you and him are the moriarty's Gang and Lestarde who only found it out after he mentioned one funny memory of you two.
His S/o is the person he loves talking to the most.
He is very observing too.
And a very good listener too.
You can also sit in silence with each other without it being weird.
@viiper1