After the globally atypical year of 2020, distance cooperation and experimentation with virtual and blended learning opportunities are becoming a standard in all educational levels. Digital teaching/learning materials are at the forefront of this movement, presenting many advantages, since these can be innovative, engaging, interactive, and can even be tailored to meet the students’ and teachers’ needs. In this context, Open Educational Resources (OER) are a powerful concept for sharing the world's resources for the common good, reflecting the international commitment to Education For All (EFA). In the past few years, the development of OER has grown exponentially, however, several are quite “closed” and few have the necessary scientific and pedagogical quality certification as real “educational” resources, particularly in the Mathematics area. This was the main idea behind an Erasmus + Project, that brought together six Higher Education Institutions (HEI) from five European countries. This project, still in development, has emerged from a practical need for hybrid and remote teaching and learning open support. Its main goal is developing an Open Digital Library of Mathematics OER in seven distinct languages, encouraging its open dissemination and use, building a truly sustainable Math education promotor. An overview of the project and its main objectives will be presented, as well as its several operational and progress challenges as well as the results that have been accomplished thus far. This project entails several distinct but complementary features that started with the construction of an OER assessment model, culminating with the development of a multilingual OER bank and its continuous sustainability. This can only be achieved with the future establishment of an OER developer’s community among Math teachers and students from several education levels, that will be engaged in other project programmed activities, as Teachers’ Trainings, Users’ International Challenge and Students’ International Competition. This Project progress and success is largely based on the interaction, input and participation of all stakeholder groups.