This is the opposite answer to what the OP is asking. He wants the zero dollars to go through on a customer which is already setup to be credit blocked and on hold because there is over the limit.
IFS won’t allow some orders to go through based on order value as an out of the box condition. It would require a custom event or program to look for customer orders at zero value where the customer is also over the limit on credit and then the function would need to auto handle the order to allow release.
If this is a condition that happens often enough to require automation, I would think there are bigger issues than the software requiring extra steps to remove the hold.