MK60DN512VLQ10 and STM32L4P5ZETx.they are the same in ARM Cortex-M4 and even in pin configurations.
The code will run on the microcontroller Core, but peripherals (GPIO, USART etc) are completely different. So you will need to rewrite all peripheral-related code. If your project structure is logical (ie if you have decent HAL - Hardware Abstraction Layer) it can be done without touching the main program logic.
But it is hard, long and unpleasant work - sometimes it easier to rewrite it from the scratch.