In 1960, the Zetor UR I series (Unified Range) was introduced. The redesigned larger 5511 was added to the lineup in 1966, and soon after, the smaller models were also designated as the "five series." However, they only received the new design and cast iron front frame later. The biggest technical innovations of models 2511, 3511, and 4511 compared to their predecessors were front suspension (optional), brake steering, and a new dashboard. Power steering was available as an option.

Familiar features from the predecessors included a dual clutch, a 10+2 transmission, and Zetormatic hydraulics with push-rod sensing. Zetor’s gearbox included an unusually slow first gear. The PTO speed for local use could be changed via the transmission. The gear lever was placed on the dashboard, and the gear layout was unusual. On four-wheel-drive models, the 3545’s four-wheel drive was only available in the high-range of the range gearbox. Only the 5545 model four-wheel drive was imported to Finland, where four-wheel drive worked on all gears. In the early 1970s, models 3611, 4611, 5611, and 5645 equipped with factory-installed cabs were also produced, but these were not imported to Finland.

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