Zimmer is one of a few Baháʼís who revived the efforts of Ruth White to oppose Shoghi Effendi, claiming that the Will and Testament of ʻAbdu'l-Bahá was forged.
Zimmer based his claims partly on the work of criminologist Charles Ainsworth Mitchell, who Ruth White had hired to review photocopies of the original Will and Testament of ʻAbdu'l-Bahá.
[4] Mitchell could not read Persian, however, and the claims of a forgery were not taken up by many other Baháʼís opposed to Shoghi Effendi at that time, most notably including Ahmad Sohrab.
Hermann Zimmer remained one amongst a small group of Baháʼís to question the authenticity of ʻAbdu'l-Bahá's Will.
Geschichte, Lehreund Organisation in kritischer Anfrage,[8] a work which Denis MacEoin notes "did indeed do a lot of damage to the public image of the Baháʼís" in German-speaking Europe and "damaged the Baháʼís and distorted their cause in certain quarters, mainly within the Catholic and Protestant churches.