There really isn't much they can do. If Israel deployed troops somewhere deep in Syria then they could be targeted (never going to happen), but Iran can't do much to halt Israeli strikes. Israel knows this and is playing it smart. If Israel steps up the strikes I wonder how long Iran will sit there before either withdrawing or doubling down...
Either way, Israel will continue to be a thorn in Iran's Syria deployment, I wonder if they are preparing some type of retaliation, because once Israel turns the heat up it won't be a sustainable situation for Iran unless they have some sort of trump card which we don't know about.