"Prior to co-founding the company" could be paraphrased as "before he co-founded the company"; it defines a moment in the past. So you need a verb in the past, not a present perfect: "Prior to co-founding the company, he worked with McDonald's / used to work ".
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AnonymousPrior to co-founding the company, he has worked with McDonald's'he worked' is good enough; 'he had worked' is a possibility if you want to put more distance between the two jobs.