I read the question differently than Disagreeable.

There is nothing whatsoever illegal about working for two different employers. There is not even anything illegal about working full time for two different employers. Plenty of people work second and even third jobs. There's no problem with that. I've done it myself, and my husband is doing it still.

The ONLY thing that would be illegal would be if you told one of the employers that you had worked hours, for that employer, that you had not. And that would be illegal regardless of whether you worked two jobs or not.