Canola (Brassica napus L.) is a major global oilseed crop whose productivity and seed quality are severely constrained by drought stress, particularly in arid and semi-arid regions. Improving nutrient-use efficiency under water-limited conditions is therefore essential to sustain crop performance. In this context, nanostructured fertilizers offer a promising strategy to enhance nutrient delivery and stress tolerance. This study evaluated the effects of two zinc sources-nano-zinc oxide (nano-ZnO) and zinc sulfate (ZnSO4)-applied individually or in combination on yield and seed quality of four spring rapeseed cultivars under different irrigation regimes, including full irrigation, irrigation interruption at flowering (severe drought), and irrigation interruption at pod formation (moderate drought). A two-year field experiment was conducted using a split-split plot design, with irrigation regimes as main plots, zinc fertilization treatments (control, ZnSO4, nano-ZnO, and combined ZnSO4 + nano-ZnO) as subplots, and cultivars as sub-subplots. The combined application of soil-applied ZnSO4 and foliar nano-ZnO consistently outperformed individual treatments, significantly increasing grain yield, yield components, and seed quality under both well-watered and drought conditions. The open-pollinated cultivar Delgan showed the highest performance, in some cases exceeding the hybrid Hyola 50. Integrated zinc application also enhanced oil and protein yield, indicating improved nutrient-use efficiency and stress resilience. These findings demonstrate that the synergistic use of nano and conventional zinc fertilizers represents an effective strategy to mitigate drought-induced yield losses and improve seed quality in rapeseed, supporting sustainable agricultural intensification under water-limited conditions.