Dec. 29, 2017, 4:07 p.m.
I like the part where it says you could use the lowest LODs of other similar looking cars that are already from the game, that's a good idea.
I know you are using Zmodeler 2 but just in case, to make some LODs in Zmodeler 1 I sometimes do this: select a bunch of vertices (or faces, and then switch to vertices mode) and click Create > Objects > Unite Select to unite those vertices and reduce the vertices count, but it can be a slow process and it can mess up the UV mapping of that part sometimes.