You are going to have to solo this mission with Matriarch only, no way to get mutagen mass for grunts this time but if you are going for it you might as well do the no upgrades one as well, it will take roughly the same amount of time with or without upgrades.

The only thing upgrades does for you is give 50+ hp, if you get spotted when enemies patrol you might as well reload so the only thing hp does for you is if you move into their alert state viewcone you can take 1-3 hits for "free".

You can in total do 3 achievements for this run, the no upgrades, no kill and mission completion.

By going into it first with upgrades you can get the Lure enemies into mech path and shoot mech with ranged unit out of the way and then start the real run.

1: you can not attack enemies directly, anything that dues due to a direct action from you counts.

2: Mech always moves first, anything in the way gets squished.

3: Any enemy that dies due to Mech does not count against you, if this is intended or not i can't say but it will happen regardless of what you do (Really dumb AI here)

4: Any enemy that sees you entering their viewcone will follow you in the direction you retreated after.

Now the way you can clear some parts of the mission is by making use of rule 2-4.

Do the following:

-When the Mech is 2 moves away from your area, enter the viewcone of an unalerted enemy, can be done once with an alert enemy unupgraded or a few times at max.

-Retreat into the middle of the area where the Mech will move in 2 turns, after your turn has ended the Mech moves closer then the alerted foe move to inspect your earlier location.

-It will now be in the Mechs path and gets squished but won't count against you so still at 0 kills.

-Can be done with all the enemies that patrol along the Mechs path, just make sure you can get into a safe location after.
+The hide boxes on below the first switch on the left can used for Machinegunner and the patrols there.
+The one patrolling in front of the main chamber door should be given priority, it only lets you sneak past there once over several turns if you don't take care of them -> can screw you over with other units paths.
+Units to the right after can now be taken care of, or you can wait until the main chamber is unlocked to have a safe place to retreat to.

Took me 87 turns to win but screwed up a few units so they got alerted and had to wait around a lot, also didn't know Mech kills didn't count when i did it so if anyone sees this you can speed things up greatly when you go for it.
Good Luck >:)

Proof below: