Considering pickers’ learning effects in selecting between batch picking and batch-synchronized zone picking for online-to-offline groceries

•The performance of batch picking (BP) and batch-synchronized zone picking (BSZP) are compared with learning effects.•The heuristic methods, i.e. genetic algorithms, are proposed to solve BP and BSZP strategies.•With learning effects, although BSZP needs to travel longer than BP, it needs a shorter search time than BP.•If pickers’ working days are long enough, the search time of BP becomes closer to BSZP, leading BP to outperform BSZP.•Which strategy outperforms mainly depends on learning rates, storage assignments, and pickers’ working days.