"make them hard to" is a grammatically correct phrase and can be used in written English.
It can be used to mean causing something to become difficult or challenging. Here is an example: "The new laws made it hard to open a business in the city."
And that will make them hard to interpret.
That was supposedly Deng Xiaoping's favorite brand, and government quotas make them hard to find.
The songs resonate with an emotional specificity that make them hard to replicate.
Mr Brown's vaunted tax breaks are hedged around with conditions which make them hard to use and of limited value.
They have sealed-in batteries and some are designed to make them hard to open, let alone upgrade.
Their roster is cluttered with underachieving players, most of them with bloated contracts that make them hard to trade.
There is a real danger in this strategy, however: keeping the fires of religiously-inspired anger burning may make them hard to douse.
The laws governing ethics and lobbying in Massachusetts have not been overhauled in years, Mr. Patrick said, and "significant gaps and weaknesses" make them hard to enforce.
But Frost did not intend his notebooks to be published, and they are filled with inserts and crossings out that make them hard to decipher.
While her group works in Russia to promote domestic adoptions, Ms. Thompson said, international adoptions remain the only alternative for thousands of children, many of them older or with disabilities that make them hard to place.
Companies are loth to hire untested and less productive young people when high minimum wages and payroll taxes make it expensive, and job-protection laws make them hard to fire.
