Yes I agree it has a bad weakness in the knees. Although unless you know the episode you wouldn't know that it has a cloaking device and makes in completely invisible. Dint don't know at all what the Irken's battle stragity is but It most likely stalks its target at a far distance. This is due to the fact that the Megadoomer is very loud and still creates foot marks in the ground. Then once in range pulls out the doom cannon (which is seen below.) We IZ fans never even got to see the doom cannon fire because it takes so much power to fire that it put the whole city in a back out.
Now for stuff related to the picture.
Im not sure what a tablet is but if you mean a picture I drew it over then yes. I drew it on paper then scanned and photo shopped. As for it being all my art, yes it is. The whole think is drawn by me, the only thing I used from IZ is pictures of it for reference.
P.S: Ive noticed some errors in the picture and will be uploading a new one.
REFERENCE:
Zim at Mega-doomer controls:

Doom cannon:
