There are different levels of zinc galvanization. If you want it to last longer, then get a thicker layer of zinc on the outside of the steel.

One way to get a thicker layer is to hot dip galvanize it. Another way is use a Simpson hanger that is Z-max plated which is basically just twice electrogalvanized steel plate and actually not hot dipped. 

If it's galvanized just a little bit, it'll technically be okay for treated lumber. If you want it to last longer, then get more galvanization on there. Zinc is a sacrificial coating, so as it corrodes it protects the steel less and the steel will begin to rust.