From the "text of executive order on eliminating rules":
(b) For fiscal year 2017, which is in progress, the heads of all agencies are directed that the total incremental cost of all new regulations, including repealed regulations, to be finalized this year shall be no greater than zero, unless otherwise required by law or consistent with advice provided in writing by the Director of the Office of Management and Budget (Director).
(c) In furtherance of the requirement of subsection (a) of this section, any new incremental costs associated with new regulations shall, to the extent permitted by law, be offset by the elimination of existing costs associated with at least two prior regulations. Any agency eliminating existing costs associated with prior regulations under this subsection shall do so in accordance with the Administrative Procedure Act and other applicable law.
So let's say you want to impose a job-killing regulation that has benefits equal to 100 and costs equal to 20. The net benefits are 80 and so you go looking for two or more existing job-killing regulations to get rid of. Their costs must be greater than or equal to 20. The magnitude of their benefits do not matter.
There is nothing in economics that leads to the conclusion that the benefits of job-killing regulations are zero. Regulations have benefits and costs. If the benefits of the regulation is less then the costs then that regulation should not be implemented. If the benefits are greater than the costs then that regulation should be implemented because it would improve the overall welfare of society.
But with this executive order, in order to improve social welfare we need to find at least two regulations (that may also have improved social welfare) to eliminate.