Yes, people can create things in Zmodeler. Blender is free and you can create things there too. Bama1234 (the modder of Montana mod) is known to use GMAX for his 3d models.
As long as you are comfortable with the program and know what you're doing, you can make anything.
When your trial of Zm3 runs out, consider doing a "downgrade" to Zm2 and try modelling things there.
Zm3 has a special advantage though: You can edit person models in there.