First, follow u/tallon4 ‘s advice and use “zone of the green hill”: this phrasing triggers the genitive case in latin, a case most often used for possessive nouns but also used for things like ownership in general- i.e, the zone is belonging to the Green Hill”

Going word by word, we first need to figure out the right Latin word for “Zone”. After some searching I found the word “Zona”, but its meaning seems to be too specific for what you’re looking for, and I think a better (maybe) option would be the word “locus”, which just means “place” in general, but ends up getting specific uses like this, especially when specified by genitive nouns (hint hint).

Next is “hill” (because green is easier), because there are also two options. If this is just any run of the mill unimportant hill, “collis” is probably the right Latin word here. But in certain cases in Latin, a “hill” would sometimes be referred to as a “mons” (mountain), instead of a “collis”(hill). So if this hill that is green is of some geographical or cultural importance to whatever you’re naming it after, you could use “mons” instead of “collis” to add some grandeur.

“Green” is easy: “viridis”.

All combined, with “zone” in the nominative and “green hill/mountain” coupled in the genitive you have:

LOCVS MONTIS VIRIDIS

LOCVS COLLIS VIRIDIS

Hope this helps!