There is one thing you should never do with TCs and that is using them on a wide lens, bad karma!
By the way Nikon does not supports or recommend this with own TCs.
I don’t know Kenko TCs, but wide lenses have rear nodal point glass behind the barrel so beware of breakage.

ok, I have to find my 18-55. It's around here somewhere. Thanks for the warnings and advice.

I imagine you'll do better with the 18-55, though I'd think a 35 or 50mm prime would serve you much better if you have one/can get your hands on one.

I also wouldn't do it, doesn't make a sens for me, instead of this I would use the 70-200

hmmm i wouldn't do it.. it will be much bigger...
TCs and wide angles usually don't play well together.. and the tc 1.5 is quite an old design i belief. so it will degrade the image even more...

A TC will surely hurt the quality and it is advisable to use them when you can't really do without them ... e.g. making a 300mm into a 450mm lens.
Though the 18-55 in notoriously poor in IQ so perhaps you should do some tests with the 18-55 and 12-24/TC combination and see if the TC brings the IQ down below 18-55 or not and then make a decision.

why would you wanna make wide angle in to zoom especial if u already have zoom ?

I am doing a photo shoot tomorrow. I was thinking of attaching my Kenko 1.5 (yes they have a one point five) TC to my 12-24 F4 for a normal FL zoom. Would this work or should I use the 18-55? I am also using my 70-200 but just wanted to know if this contraption would work.