Stories vary about the exact circumstances of this. Some say Zeus set up Aphrodite to fall in love, others say she chose out and seduced the mortal. If it was Zeus who set it up, we have to explore the exact reasons for this given how he called Hephaestus a fool.
What is Zeus’s plan here? Is this another attempt at getting her to settle down and tame her lustful ways? I’m not sure that logic works because she’s used up three different gods and still hasn’t satisfied her lust. How is a mortal going to take care of her?
Maybe it’s to kind of get her in the family business? When Zeus has his affairs—with goddesses and mortals—he sires children. Aphrodite ends up giving birth to a lot of children, herself, both gods and demigods. Does he secretly want her having children? It’s possible. This is an act of creation such as Zeus has done himself, so it does bring more order to the universe by increasing the number of gods and providing heroes for humanity to emulate.
To modern readers, it seems very odd to set up a daughter to fall in love with a person, encouraging that daughter to cheat on her husband. Zeus, though, doesn’t exactly fit the bill for father (or husband) of the year.