Little is known about Bakton Zhonnu Tsultrim (bag ston gzhon nu tshul khrims). He was initially a student of Tibetan masters before going to Kashmir, Nepal, and India to study with many paṇḍitas there. He studied Sanskrit and translated many scriptures and treatises into Tibetan.
Among Zhonnu Tsultrim's translations are the Vajraśikharatantra, in the Kangyur; the Ming mdzod lists over twenty translations of treatises and liturgical texts in the Tengyur relating to various tantric systems such as the Māyājāla and deities such as Vajrapāṇi (phyag na rdo rje gos sngon).
The Blue Annals also lists him in a Vajravārahī transmission lineage, which he received from Rongpa Serseng (rong pa ser seng, d.u.) and gave to Takton Zhonnu Pel (tag ston gzhon nu dpal, d.u.); a Mahākaruṇika transmission that he received from Tagton Zhonnu Dar (sag ston gzhon nu dar,) and gave to the Kagyur master Tel Khenchen Sherab Dorje (thel mkhan chen shes rab rdo rje, d.u.); and Kacho Nyendrub (mkha' spyod bsnyen sgrub), which he received from Yungton Dorje Pel (g.yung ston rdo rje dpal, 1284-1365) and gave to a Lama Tsulgyal (bla ma tshul rgyal) of Nartang (snar thang).
Zhonnu Tsultrim was also a disciple of Lotsāwa Chokden Lekpai Lodro (lo tsA ba mchog ldan legs pa'i blo gros, d.u.) and Sherab Sengge (shes rab seng+ge, 1251-1315), a Sakya Kālacakra and Prajñāpāramitā master.
In the image here Zhonnu Tsultrim is reading a text titled Khorlo Demchok Khandro Gyatso ('khor lo bde mchog mkha' 'gro rgya mtsho), a work associated with the Dākārnava tantra.
Bibliography
Grags pa 'byung gnas and Rgyal ba blo bzang mkhas grub. 1992. Gangs can mkhas grub rim byon ming mdzod. Lanzhou: Kan su'u mi rigs dpe skrun khang, pp. 1505-1506.
Roerich, George, trans. 1996. The Blue Annals. 2nd ed. Delhi: Motilal Banarsidas, pp. 396. 1007, 1043.