AN fittings??

Zinc and aluminum don't play well together. I'd stick with all steel and brass, or all aluminum and brass. Cadmium is the right plating to use on steel to avoid problems with aluminum. Type II decorative anodize isn't dielectric enough for me to be comfortable with it against zinc plated parts, personally.

It's not guaranteed to cause a problem, but with stuff that can burn or explode I'd rather be safe than sorry.