Z20T is well suited for hot landing zone. Providing suppression fire and deliver the assault troops but they should not be loitering around after the troops disembarked, that task belonged to Z10/Z20, or attack drones in the vicinity.
Ermmm ... expanding on what
@Blitzo said.
For a Z-20T loaded with rockets and troops - Troops are the first priority. If you have a hot LZ, you don't dick around unloading ordnance on targets you haven't even identified until they starting shooting at you. A helo is a lot of empty space that can take bullet sized hits with no effect. But that empty space once loaded with troops ... using troops as bullet sponges is not good sustainable practice.
If you really had to assault a hot LZ - usual practice is for single-role assault helos/gunships/aircrafts to prep the zone and draw out firing positions before the single-role troop transports go in low and hard while defenders are distracted/suppressed. If you have dual-role assault/troop helos, they go in and disgorge troops first before circling around and unloading ordnance on identified defenders.
A lot of people assume that air assaults into LZ are uncontrolled ingress-egress flights ... for medium to large LZs, this far from the truth. Like any FARP Airbase - ATC rules actually exist and there is a virtual runway with a landing path/vector and take-off path/vector (not to mention in this case, further complications of segregation of fire support aircrafts). So if your Z-20T is making a rocket run, it will have to make the run and circle around to enter the LZ from the correct approach - not fly into the LZ as they please - that is just begging for collisions to happen. Circling around with troops in the cabin? Not a good idea. Better to land the troops then join the CAS stack to be vectored in by the FAC either on ground or flying overhead.
One last thing - what useful range does a Z-20T have once you load up a full complement of troops and rockets? Enough to keep up with the main assault element that is say Z-20 with just troops? For sure, that depends on mission parameters but once the range opens up, this option is no longer available