Paul,
By allowing all devices on the DMZ networks to initiate communications with devices on the internal network make the use of DMZ networks useless. The whole idea is that you place servers in a DMZ to protect your inside resources.
In case you decide to go ahead with it, you could use the following solution. Replace the IP address I use in this example with your real inside IP addresses (and mask)
static (inside,dmz1) 172.16.1.0 172.16.1.0 netmask 255.255.255.0
access-list dmz1 permit ip any any
access-list dmz1 permit icmp any any
access-group dmz1 in interface dmz1