In private sector, Zainudin started as Production Executive in a manufacturing outfit. He later moved up the hierarchy to more senior positions such as Manager, General Manager and Senior General Manager in big corporations including those within DRB-HICOM Group and UMW Toyota Motor.  

Since 2007, Zainudin has ventured into provision of training services and set up Budiman Dinamik Sdn Bhd.  He is a Certified Trainer registered with Human Resource Development Fund (HRDF) bearing registration No. TTT/0898. He regularly conducted training concerning trainer development such as Sijil Kemahiran Malaysia (SKM) Tahap 3 Operasi Latihan Vokasional (Vocational Training Operation - VTO), Train The Trainer, Strategic Training Analysis, Developing Effective Training Modules, Evaluation On Effectiveness of Training, Public Speaking and Effective Presentation. He also conduct training on human resource management such as Understanding Employment Act, Fundamental of HRM, Sexual Harassment at Workplace, Managing Discipline At Workplace, Conducting Domestic Inquiries, Conducting Performance Appraisals, Setting Up KPI, Leadership Skills and Supervisory Skill.

Zainudin also conducted training on productivity improvements such as Implementation of Effective 5S and Innovative and Creative Circle (ICC). On occupational safety and health, he conducted training on Enhancing Safety At Workplace, Setting Up Effective SHE Committee, CBT On Safe Handling of Forklift and CBT On Safe Operation of Over Crane.

In consultancy service, Zainudin provides consultancy on human capital development as well as human resource management such as conduct review of compensation and benefits, preparing employee handbooks and conducting training needs analysis. He also provides consultancy service on implementation of 5S and ICC.

Among organisations have been benefited from Zainudin services are DRB-HICOM Group, Padiberas Nasional Bhd (BERNAS), Ramsay Sime Darby Healthcare College, Perodua, Johor Port Berhad, Ingress, TS Lear Automotive, SAJ Holdings, Inokom, JVC Malaysia, Dommal Food Services, Top Thermo Mfg, Tatsumori, Institut Kemahiran Industri Melaka, Adabi, Rapid Bus, Mr DIY Trading, Caregiver Academy and many others. For government sector, he conducted programs for Min of Sport & Youth, Min of Defense, Min Rural Development, MARA, Public Works Dept., CIAST, Sarawak’s Institute of Agriculture, Felda, Institut Latihan Perindustrian and Institut Kemahiran Belia Negara. He also had opportunity of conducting training in Brunei.

Currently Zainudin is resource person to HRDF for modules on Train The Trainer and Evaluation On Effectiveness of Training. He also associated with various training institutions such as Malaysia Productivity Corporation, MARA, Universiti Teknologi Mara, Universiti Teknologi Malaysia and Universiti Tun Hussein Onn Malaysia.

Academically, Zainudin holds MSc (University of Plymouth, UK), B.E (Mech) (UTM), Diploma Lanjutan Kemahiran Malaysia (Pengurusan Hubungan Industri), Diploma Lanjutan Kemahiran Malaysia (Pengurusan Pentadbiran), Executive Diploma (HRM) (UTM), Diploma Public Management (INTAN), Diploma Kemahiran Malaysia (Pengurusan IKS), SKM3 Material Handling Equipment and SKM3 Freight Forwarding. In training, Zainudin holding Diploma Lanjutan Kemahiran Malaysia (Pengurusan Latihan Vokasional), Diploma of Training & Assessment from Australia and SKM3 Pegawai Latihan Vokasional (Vocational Training Officer - VTO). Currently he is undergoing PhD program at UTM in the area of TVET.

Zainudin is registered as Graduate Engineering (Mechanical) with Board of Engineers Malaysia (BEM) and as Professional Technologist (Manufacturing and Industrial Technology) with Malaysian Board of Technologist (MBOT). As part of his social responsibilities, Zainudin served as Panel Member for Industrial Court (Representing Employer) for period of 2004 – 2006. He also sit in the Governing Board of Malaysian Institute of Retirement Management (MIRM) since 2018.