Highly Skilled Migrants are allowed to change employers while their residence permit is till valid. The residence permit continues as long as you fulfil the conditions, even if you change employer or obtain another position.
If you no longer work for the employer or change your position, your employer must pass this information onto the IND. Have you found another job? Then you must inform the IND yourself of your new employer. You must do so within 4 weeks. The IND will then review whether the conditions are still being fulfilled.
When your employer terminates your contract before the end date, the IND gives you 3 months to find a new employer and apply for an extension for your residence permit. If you do not find a job within these 3 months, you must leave the country. You can find more information about your rights as a highly skilled migrant and what you can do in case your company terminates your contract before the end date, and what steps you can take next by clicking on losing your job in the Netherlands.