Apply for a patent before applying for trademark registration. . . Because patents need novelty, you can't apply for a patent after the trademark registration process is made public. Because it is a design, it may be successful without a real trial, but it is easy to be invalidated in tort litigation.
In addition, there is no need to apply for a trademark. However, it can be registered and filed, and it can be used against a bona fide third party after filing.