It all depends if you want to "hide" the source ip or/and if you coming from the private ip address to the public or vice versa. from DMZ to LAN (assuming you do have a private ip address range), if you want to "hide" the DMZ server source ip address then you can NATed to the PA LAN interface so all request will appear for the LAN users as PA source ip. NAT is not a requirement between the rfc 1918 ip addresses but it is between the public ip as private ip are not allowed on Internet.
Can you explain what you are trying to do a little bit more, and what your current infrastructure looks like. You may be thinking about a u-turn NAT or hairpinning but without knowing what your setup looks like we can't give you an answer for your enviroment.
Generally the respective zones would just need security policies put into place to allow the traffic.
As everyone has mentioned, if the hosts are communicating on their connected internal addresses all is good.
But I suspect you may be referring the the case where internal hosts get DNS entries with the external address of the servers in your DMZ. Then you do need to use what is called "U turn" NAT for the connections to work.
See this documentation.
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