Developing high-yielding and resilient maize hybrids is essential to ensure its sustainable production with the ongoing challenges of considerable shifts in global climate. This study aimed to explore genetic diversity among exotic and local maize inbred lines, evaluate their combining ability, understand the genetic mechanisms influencing ear characteristics and grain yield, and identify superior hybrids suited for timely and late sowing conditions. Seven local and exotic maize inbred lines were genotyped using SSR (Simple Sequence Repeat) markers to assess their genetic diversity. These diverse lines were utilized to develop 21 F1 hybrids using a diallel mating design. These hybrids, alongside a high-yielding commercial check (SC-10), were evaluated under field conditions across two growing seasons under timely and late sowing conditions. The results showed that sowing date, assessed hybrids, and their interaction significantly influenced all measured agronomic traits. Notably, late sowing reduced plant height, ear characteristics, and, ultimately, grain yield. Several hybrids, particularly L101 × L103, L101 × L105, L104 × L105, and L104 × L107 under timely sowing, and L101 × L105 and L104 × L107 under late sowing, surpassed the agronomic performance of check commercial hybrid. Inbred lines L101 and L103 emerged as superior combiners for ear traits and yield, while line L106 showed promise for breeding shorter-stature plants. Hybrid combinations L101 × L105, L104 × L107, and L106 × L107 were identified as specific good combiners for grain yield and related traits under both sowing conditions, indicating their potential for commercial development. Strong positive associations were observed between grain yield and certain agronomic traits highlighting their utility for indirect selection in early breeding generations.