This is what support told me when I asked them a similair question.
"It is possible to set serial value for dns zone to zero (4294967296) and wait until other dns-servers refresh their information and only after it update your dns-server with new serial, as decribed here in chapter 7:
http://www.faqs.org/rfcs/rfc1982.html
Please read that documentation before implementing what I suggest.
I suggest doing follow steps:
1. Deny all changes for your dns zones (you can make it by canceling permission "DNS zone management" to all of your clients for 2 days) .
2. Set serial for all zones to 4294967296 (232) both master and slave servers. You could create a script or do it manually.
3. restart named.
4. Wait until all the dns-servers in the world take this serial. It depends on
your $TTL of zones ( by default it is 86400 = 1 day )
5. Rebuild all the zones to set standard serial back:
# export domains=`mysql -Ns -uadmin -pPASSWORD -Dpsa -e"select name from domains"`
# for i in $domains ; do /usr/local/psa/admin/sbin/dnsmng update $i ; done"
Hope this helps.