Module D is based on international standards for management systems, and indeed ISO 9001 is an EU harmonised standard for proving compliance against quality management requirements.
At the same time it is not required for you to have ISO 9001 certification to get Module D certification.
A company does not need any prior certification against a management system standard. It is however possible that prior certification under ISO 9001 may make the cost of certification lower.
But it does make things significantly easier.