Can I use 1/4 inch cork to equalize floors before installing laminate flooring?
There is no way I would use a cork underlayment to make the floors equal.  Cork has too many expanding properties.  I don't even think you could get the cork to "sit" under a thin laminate.  Also cork will feel softer than most other forms of underlayment.  To the point where your floors will feel different.

I would use plywood or what is under higher floor (probably plywood).