This disorder (abiotic disease) happens when the flower anther sticks to the developing fruit as it grows. Characteristic symptom is a thin brown longitudinal scar with transverse scars resembling a zipper. It extends down the fruit. There may be more than one scar on a fruit. An open hole may develop next to the scar. Affected fruit remains solid and eatable; rot does not ensue.
Zippering is more likely to occur during cool weather. Some varieties are more prone to this disorder.
The only option for controlling this disorder is to grow varieties not prone to zippering.
Wapsipinicon Peach with zippering
Black Zebra fruit with open hole plus characteristic zippering symptom. Cracking is not a symptom of zippering.