Zenderoudi's interest in lettrism developed further in the later 1960s and his focus turned turned towards the Persian letterform as the sole motif on his canvases. The other iconography from his Saqqa-khaneh phase fell away -some to be later revisited- and the compositions consisted solely of indecipherable Persian words, superimposed on each other or in variety of scales, deliberately distorted and subverting the rules of callligraphy. Around the turn of the 1970s Zenderoudi's paintings entered a new phase, and compositions focussed on single letters or groups of letters repeated endlessly to create rythmic patterns against a white field. The resulting works are markedly restrained compared to what had come earlier. Starkly beautiful, they form the the most minimal phase of Zenderoudi's oeuvre.