Timeline for Zero1 sim delivery, based on my own experience of 2 port in, plus a sample from gapboy.
If you apply late in the day or after office hour, it will count as the following business day.
Zero1 takes 2 working days to approve & sent "mail out" email, that appears to be sent out ~8am.
It usually given to Singpost a day after the "mail out" email around 1500-1700.
Singpost usually delivers the following business day.
All in all 4 business days from application to delivery.
So unless you apply on a Monday, otherwise you can expect it to cross the weekend.
If there is a public holiday, add a day to that.
This is not even counting any sort of peak or surge, so plan that into the schedule.
if you need to meet some port in or port out deadline, remember to include the porting time into account.
If anyone has experience that differs from this, would appreciate your feedback and possible reason behind it.