If the daughters of Tzlofchad got married so late, how did they have children? A miracle happened to them and it is compared to Yocheved giving birth to Moshe at an old age. The gemara explains the whole chronology of the Yocheved narrative and how it is clear she was so old when Moshe was born. In telling the narrative, they also resolve other difficulties in the verses. The daughters of Tzlofchad are mentioned twice in a different order each time. The gemara explain what one can learn from this. The daguhters of Tzlofchad were able to marry anyone they wanted, yet it was recommended they marry within the tribe. however, a commandment was given to the other women in their generation who inherited land that they could only marry within their tribe. This was a commandment only for that generation. The gemara explains from words in the verse how we know it wasn’t forever and then questions that explanation based two other places where the same words are mentioned and the commandment is also for future generations.