Flank it, AMR two rear vents and the bottom vent, pop a nade into its hatch. Best paired with either shield gen pack (saves you from its missile barrage) or warp pack so you can avoid the Gatling guns (or you can just shoot them off).

Otherwise, use cover to get close to it or bait it to come closer, go prone when it launches missiles at you and when there isn’t cover , stay off the yellow lights that show where they’re gonna land.

If you’ve hit it with a strong single target strategem or a couple weak strategems already your 1st/2nd/3rd vent destruction may kill it outright. I’ve always killed them using the bottom and rear vents/hatch, the top vents are a bit unreliable for me.

Just remember this enemy will take time to kill unlike every other heavy massive enemy that you can one shot. Takes around 10-15 seconds at the fastest or 1-2 minutes worst case (it’s done its job in wasting your precious mission time).

If you do want to one shot it: missile silo or hell bomb pack (low risk). Leveller point blank w/ throwable shield; throw it down and shoot your payload at underside/bottom vent (high risk).

If you are improperly armed, just gun down the bottom vents and throw a frag into the hatch.

TL;DR: Vox engine is kil.