how easy is it tohack iphone6

If it isn't jailbroken, extremely difficult. Only one company claims to have been able to do it.

To put it in perspective:

The FBI paid several millions to have a company break into an iPhone. Took them specialized equipment, several weeks and physical possession of the device to accomplish.

And to put it in more perspective, the phone that was opened for the FBI for a rumored $800,000 was an iPhone 5c and did not have the security enclave firmware/chipset that is in the iPhone 6.