That's a very good looking Z you've got here,
Some very cool mods, and a decent understanding of lighting and brushing

Night time backdrops are very hard to get the paint looking good on though, especially in strong artificial lighting like this. I think the main problem here is that the paint looks a little too saturated (too strong a red colour - it needs more whites and pinks and darker areas). Basically just more contrast between your light and dark paint colours.
The wheels (especially the rear one) need a lot of work too

The rear one is very blurry, and the wrong angle - if you find that the wheel you want doesn't fit both arches, then usually you just have to find another
I'd also suggest learning to use the pen tool, then you can add a slight feather and get smooth selections without the 'jagged' edges. I'm working on a tutorial for tthis right now.
You're very close to being inter standard, just not quite there yet. Looking at your other chops this becomes apparent too. I'd like to see a few more chops of this standard, but with the mistakes ironed out before I think about a promotion though, keep it up