I get that Garak was a lot older than her, but I wasn't squicked out, mostly because the (romantic) affection seemed rather one-sided. Garak was very gentlemanly towards her and would always playfully make light of her feelings for him when she tried to the turn the conversation to that. They never got past that whole hand-pressing thing they would do sometimes (which is the Cardassian equivalent of holding hands, I guess?). Also, the one time they kiss, it's clearly Ziyal who initiates it, while Garak looks almost uncomfortable.
I really can't fault Garak for being spending time with Ziyal. He was lonely, and she was the only other Cardassian on the station. I think Garak was drawn to her innocence and naivete, and that he was drawn to Bashir for much the same reason. Both of them are such a contrast to his cynical, secretive worldview. Garak also seemed positively baffled by the idea that Zyial could be in love with him. I still remember the exchange between him and Kira in "Sacrifice of Angels" when they're in the infirmary with Ziyal's body:
Kira: She loved you.
Garak: I never understood why. *strokes Ziyal's face* Now I suppose I never will.
*sniff*
All that being said, I think a romance with Jake could have been interesting, especially when their respective fathers were at odds. I imagine Sisko would be pretty ok with the relationship, but I'm sure Dukat would see Ziyal's involvement with the son of his enemy as a "betrayal," much as he did Ziyal's "relationship" with Garak. That could have been an interesting dynamic, and probably could still have worked even if Ziyal and Jake were just friends.
