Liquid Green,
Regarding the zenith points, let me use them as an example of the correct technique of ACG interpretation.
Yes, the Zenith points are especially strong because they represent the Longitude point of focus of a Planetary Primary Line. But we have much more to take into account than simple Longitude Focal Point!
Let's suppose for example you have Venus on the Midheaven Zenith Point at Tahiti Island, French Polynesia; Longitude 149 W 27 by Latitude 17 S 37.
If you have no line crossings anywhere on Earth that occur near Latitude 17 S 37, then you will have a purely Venus Midheaven Influence on Tahiti Island. So Tahiti Island will indeed be a lovely place for you to holiday and possibly even find a romantic interest.
Now let us instead suppose that at Latitude 17 S 40, and halfway across the Globe somewhere, you have a line crossing of Jupiter and Venus. Now Tahiti Island packs a double dose of Venus and the added benefit of Jupiter! Are you ready to win a windfall of money on Tahiti Island? It could happen here!
Or instead of a Jupiter / Venus line crossing, suppose we find at Latitude 17 S 32, just 50 miles East or West of Tahiti, that you have a line crossing of Mars / Venus. Now you can expect a VERY sexy encounter when you visit Tahiti Island!!! The Mars / Venus line crossing will act as "appetite enhancement" and you may find yourself feeling more aggressive and even competitive than you normally are with both men and women alike!
So you see, the line crossings add all sorts of color and flavoring to one's Primary ACG Lines and the line crossing effect covers a ring of Latitude around the entire Globe!
You should never assume that if you have a Sun Line someplace that you will be happy and successful there. If a Saturn / Neptune line crossing also impacts the latitude of that Sun Line Location, feelings of gloom and doom will haunt you constantly at that location.
With these examples, you can appreciate that both Longitude and Latitude should always be taken into account together.
As for Astro Numeric Service, see their website:
http://www.astronumerics.com/
The map ordering information is at the top right of their homepage.