Legal Question in Employment Law in California

Is that legal?

Depends upon whether an actual change of companies occurred, and whether the new company legally assumed the obligations of the old company, and whether the old company actually owed you money, and whether you quitting disqualifies you from payment under the company rules. You should have asked about all those issues before quitting. The best you can hope is to file a claim at the Labor Commissioner and have them decide in your favor.

It is rare that I disagree with Mr. Nelson, but this is one of those rare moments where we disagree somewhat.

Once accrued, vacation cannot be taken away and must be paid. The fact that you have been designated a "new employee" does not change the fact that someone owes you for your vacation time accrued. There may be some question as to whether it's the old company or the new one, but there is no question but that any accrued vacation is owed by someone.

In California, there is a law called the Private Attorney's General Act ("PAGA") that allows an action to be brought on behalf of all employees that are due wages. It may be that a labor lawyer would be interested in representing you in such a claim. Payment for your two weeks' vacation time is a matter for small claims court or a relatively small claim before the Labor Commissioner.