// Entity
#[ORM\Entity]
class ExerciseResult
{
    /**
     * @var Collection<int, CoordinationComponentResult>
     */
    #[ORM\OneToMany(mappedBy: 'exerciseResult', targetEntity: CoordinationComponentResult::class)]
    private Collection $koordinationComponentResults;
}

// Dtos
#[Map(source: ExerciseResult::class)]
class ExerciseResultDto
{
    /** @var CoordinationComponentResultDto[] */
    #[Map(source: 'coordinationComponentResults.toArray')]
    public array $coordinationComponentResults;
    // ...
}

#[Map(source: CoordinationComponentResult::class)]
class CoordinationComponentResultDto
{
    public int $id;
    public int $reachedScore;
    public float $accuracy;
}

$mapper = new ObjectMapper(propertyAccessor: PropertyAccess::createPropertyAccessor());
$exerciseResultDto = new ExerciseResultDto();
$mapper->map($exerciseResult, $exerciseResultDto);

 #[Map(source: 'coordinationComponentResults.toArray', target: CoordinationComponentResultDto::class . '[]' )]
public array $coordinationComponentResults;