Zinovii Onyshkiv was born on 30 March 1954 in the village of Zarichia, Husiatyn Region, Ternopil Oblast, Ukraine. After graduating from an 8-year school in Zarichia, he was admitted to the Chortkiv Pedagogical Specialized School that he graduated from with honours in 1973 being awarded the major «a junior school teacher». In 1973-1974, he worked as a math teacher in a comprehensive school in the village of Tovste. In 1974-1979, he studied at the faculty of mathematics and physics at the Ternopil Pedagogical Institute. In 1979, he graduated from the Ternopil Pedagogical Institute with honours with a major «teacher of mathematics and physics». In 1979-1981, he worked as a math teacher at an 8-year school in Zarichia and in 1981–1982 he worked as a junior school teacher at the comprehensive school №13 in Ternopil. In 1982–1987, he worked as a Junior School Department Head of the Ternopil Regional Institute for Improvement of Teachers' Qualifications. In 1987–1990, he was a PhD student at the Research Institute of Pedagogy of Ukraine.

In 1991, he defended a PhD thesis entitled «Didactic Conditions for the Preparation of Junior Pupils for the Study of New Material» and was awarded a PhD degree in Pedagogics. From 1990 he has been working at the Department of Pedagogics and Methodology of Junior School and Pre-School Education of the Ternopil Volodymyr Hnatiuk National Pedagogical University. In 1993-1994, he has been working as a deputy Dean of the Department of the Preparation of Junior School Teachers, and during 1996-2005 was head of the Department of Pedagogics and Methodology of Junior School and Pre-School Education.

In 2016, he defended his doctorate dissertation entitled «System of Preparation of Future Teachers for Work in General Educational Institutions in Rural Areas».

He has written over 100 scientific publications on the problem of junior school education, organization of educational process in a small-size junior school in rural areas and the preparation of future teachers for the work in such educational institutions.