Based on the established lore the Robotech Masters Empire lifted off and headed to Earth thus beginning the 2nd Robotech War. The Robotech Empire is still at War with the UEG/UEEF.
The left behinds, or Tirolians were left to fend for themselves. When the UEEF arrived that is who they found. The sick, the old, the incredibly young and the indigent. Basically anyone who the Robotech Masters didn't think would be an asset were left behind. Over the years a the young grew to repopulate the middle ages in society but the disparity still exists.
The Planet of Tirol is many things depending on who you ask but for all intents and purposes Tirol is a CAP (Coalition of Allied Planets) Protectorate administered by the UEEF and the Sentinel Council. UEEF runs the show and makes the rules in matters of defense and resource allocation (usually towards defense) while a Provisional Government of Tirolian natives work with their Governors, Legates and other landowners.
Of course now, they are under Haydonite rule and the fate of those left behind is unknown but presumed shitty.
As for the Zentraedi they are still considered 3rd class citizens and or slaves by the majority of the Tirolian people. Even the most enlightened still look at them as their 'creations'. Much of the antipathy stems from the fact that as beaten down as the Tirolians have been, to look at the Zentreadi as lesser serves an important if not wholly unfair social mechanic. Simply put, its easier to go along with life if you know that someone is still beneath you in some way. This attitude is prevalent amongst the rural populations and among certain circles of elites.
The Tirolians that have had closer contact with humans have had their views tempered by reality and experience, and those that fought besides one an other against the Invid and now the Haydonites share the bond that only soldiers posses.
In terms of interactions, it's mixed, many resent being subservient to humans, while others respect them and are grateful for their help in ridding them of the Invid. Of course, some might be bitter now that the humans weren't able to stave off the Haydonites, but most with an open mind and possession of base logic understand that ALL parties were fooled by the Shadow.
As to the newly created Zentraedi soldiers, the situation is a little more complex. Those left on Tirol would have been a rear guard of the worst kind. Stationed there as a speed bump and diversion, meant to fight and die and give the Invid the impression that they had completed their goal of wiping out the Robotech Masters. They were not expected to win, but to fight long and hard enough to be convincing.
Those Zentraedi might be a little lost. After all, they did what they were told to, and they somehow lived. I do not think that any of them would be thankful of the UEEF or towards humans, after all, it's their job to die at their Masters whim, just so happened that they didn't this time around. ALL would have stayed in the military as part of their original orders. "Protect Tirol to the death."
To that end, the new clones would defer to Tirolians as their rightful and programmed masters. A attitude that humans and assimilated Zentreadi might find odd.