You can always try gundam.info . That's Bandai's official Gundam site. You can also try
their official YouTube channel. It has been rotating, usually sub-titled, the various series. I believe both Zeta and ZZ have been in the most recent rotations.
Edit: I was on my phone when I fist posted. Added a link to the youtube channel. As of this posting, only Build Divers (multi-Sub), Build Fighters, BF Try, BF GM's Counterattack/Battlogue, IBO (Both seasons), OO (Sub), Wing (HD Remaster, Sub) and Endless Waltz (OVA Dub & Sub), Unicorn, Origin V, and 1st Film comp of Thunderbolt are up for viewing.
I know SEED (Remaster), SEED Destiny (Remaster), Zeta, and ZZ have also been available to view. Usually there is a change every couple of months of something rotated in/out.