Our profit sharing at Delta is withheld at the Federal rate of 25% and then it's taxed at whatever rate you qualify for when you file your return for that year. So if you end up in a bracket that has a higher rate than 25% then you end up owing more. If less, you get some of that 25% back.
This debate has occurred in depth over in the Endeavor sub-forum and then general consensus is that these type of bonuses are treated the same way. I'd be surprised if ZW treats them differently.
Talk about first-world problems. In the end it's a great problem to have to deal with!