Serious option: Kill them off before they can retire.
Depends on how far down the authoritarian slope the government has slipped, but it's easier to arrange a few thousand a military funerals, widow pensions, and a nice memorial, than to explain all that.
If there's oversight and war reporters and helmet cameras and no press censorship - this isn't going to happen. But I'm including it for completion.
Point to signed consent forms.
This is what will happen to those who were modified by the surgeons. Hands will be washed of the issue because they consent to it.
That it was allowed will be an issue, which will be dealt with:
Scapegoating
The general who decided to modify humans, and perhaps the general who lost the battle which resulted in the largest zombie hoard, will be expected to fall on their sword. They will submit their resignation and the government will try to wipe their hands of the issue.
It wont work entirely, there will still be angry people out there, which will be deflected by...
Hold a multi-year enquiry
Politicians do this ALL THE TIME, "let's not get mad now, lets empower some researchers to interview everyone and gather all the facts so we can make an informed decision later." By the time the 500-page report arrives, a new government is in command, anger has died down, etc.
These enquiries don't do much:
- Australia's current bushfire royal commission is forbidden from considering climate change as a factor in the devastating 2020 bushfires, despite the hottest 10 years on record being, in order: 2016, 2020, 2019, 2015, 2017, 2018, 2014, 2010, 2013 and 2005.
- In the 1980's, several Australian Aboriginal people who had been arrested were found dead in police cells under suspicious circumstances, this spawned basically an Australian version of Black Lives Matter, which was deflected with a royal commision. 432 Aboriginal people have been killed in police custody since, and they remain, per capita, the most incarcerated persons on the planet.
While you're waiting on the conveniently delayed report...
Give everyone medals, veterans discounts, call them heroes, and then ignore them.
Quoting Justin's comment, as I can't add anything to it:
Based on the track record of the American government in returning Vietnam vets, they would get everyone to say 'Thank you for your service', give them all medals, make them heroes, and then wipe their hands of any further involvement or responsibility. What is the difference between them coming back the way you describe and coming back in a wheel chair, or with PTSD, or with limbs missing? A broken body is a broken body. No need for any different response than the current one.