Breeding A.I. or natural, breed as soon as the cow comes in heat. However, the first heat post partum is "normally" not as good of a heat.
My ET Vet recommends, concerning inserting CIDR's...
1. For breeding a donor for a flush wait 60 days post partum.
2. For A.I. breeding or synchronizing wait 45 days post partum.
3. However, he says you can do 35 days post partum, however the conception rate may fall.