Sure it can. Upgrade it to v7 and then follow this link:
http://www.cisco.com/univercd/cc/td/doc/product/multisec/asa_sw/v_7_2/conf_gd/general/intparam.htm#wp1051819
Basically set up a trunk port between the PIX and the switch. Let's say you plug that trunk port into Fastethernet0 on th ePIX, your config then looks like:
interface fastethernet0
no shut
interface fastethernet0.20
vlan 20
nameif inside
ip address x.x.x.x
security-level 100
interface fastethernet0.30
vlan 30
nameif dmz1
ip address y.y.y.y
security-level 50
interface fastethernet0.40
vlan 40
ip address z.z.z.z
nameif dmz2
security-level 60
You can just add as many sub-interfaces as you like, and add that vlan to the trunk from the switch. The PIX treats these sub-interfaces just like any separate interface and will route between them as normal. Same security level procedures apply just like any other interfaces on the PIX.