This is nonsensical. What exactly did Zynga do that was so bad? They are still making hundreds of millions of dollars per quarter. That's something most companies will never do. It's not like they committed fraud or anything illegal.
As well, regardless of what you think of Zynga's games or their business strategy, the engineers have really great skills in dealing with some very great technology and high-load situations. They will be extremely marketable.
To paint every single employee with the same paintbrush just because their business isn't something you particularly enjoy is dumb.
That's unfair on the employees. Sure, Zynga has a reputation as a scummy company with low morals, but I don't think it has a bad technical reputation. And the day-to-day programmers, architects and designers won't have had much influence on the behaviour of the company. I don't think they'll be tarnished, and it would be dumb for a potential employer to reject them just because they worked there.
In the 90s when boo.com imploded (you might not remember them but they were huge) my company wanted to hire some of them. I prevailed against it then. Boo collapsed because they partied their way through their investor's money. Regardless of any other skills, they all had a spectactularly poor attitude to other people's money. You don't want that kind of culture to take root in an organization.
That looks narrow-minded for those particular employers though. The leadership might have made a lot of questionable decisions, but I don't think that should affect the quality of the engineers from that company.
That doesn't make sense, just because a company has a history of making bad management and product decisions doesn't mean the engineering talent is subpar.