The zygote is formed by the fusion of a haploid male and female gamete; Thus to determine the number of total meiotic division to produce 100 zygotes the total number of meiotic divisions in males and females should be considered.
In males: One meiotic division forms 4 male gametes, thus 25 meiotic division gives 100 male gametes.
In females: One meiotic division forms 1 egg cell, as the remaining 3 degenerates to provide nutrition to the developing egg cell. Thus 100 meiotic division gives 100 egg cells.
Hence, the total number of meiotic divisions needed to form 100 zygotes = 25 meiotic division in males + 100 meiotic divisions in females = 125.