I think it’s a good idea if there are zaps worth 0 sats to replace it because no one likes the idea of pressing “like” on a post that has really bad news for example. Likes are a mechanism to increase post visibility and it seems overly complex to have two different forms of the same thing. Another approach is I think if you are giving someone $ then you are proving you like the post so maybe the icons should be switched and then the total for both would be counted as zaps.