Think of it as a matter of accuracy.
Zero is often used as a point of reference, sometimes called "the origin". If you aim for zero, there's only one precise place you can succeed: zero itself. Zeroing in implies a high level of accuracy, the idea being that your delta from the target approaches zero.
Home, OTOH, is not a precise point in space; it's a more general area -- you can be at home in your living room, kitchen, etc, so to home in on something means you're trying to get within some reasonable distance of the centroid of that which defines "home" ( a house, a parcel of land, a planet, some region with area or volume ).