It's possible, but I'd avoid it. I bootstrapped a startup while employed at a large (~500 person) company and let the company go in the wrong direction too long

It's possible, but I'd avoid it. I bootstrapped a startup while employed at a large (~500 person) company and let the company go in the wrong direction too long because of it. Later I joined a startup where the CEO was still employed at a company he'd founded previously. I don't think either company failed solely because of the other commitments, but we will never know what opportunities were missed because of them.