Organometallic reagentss come from large tribes, and there are always wild cousins up in the hills. A good place to look for the livelier ones is in the simplest alkyl derivatives, and you should go all the way down to the methyls if you want to know their real character. Ignore the halides. Methylmagnesium bromide you can get in multiliter kegs; they might as well sell it in Pottery Barn.
Dimethylmagnesium, though, is not an article of commerce. I've made it myself. So although it's definitely something you want to keep an eye on, I can't very well say that I won't work with it. And the other metals? Dimethyl mercury I will not get within yards of, for very well-founded reasons. Trimethylaluminum is a flamethrower extraordinaire, with a solid reputation among pyromaniacs. I've used the stuff, although I wasn't whistling while I was syringing it out. Handling it in solution, as I did, is less stressful than using the pure stuff - I'd definitely want to sit down and think about that one.
But neat dimethyl zinc. . .no, I don't think so. A colleague of mine made some in graduate school, and came down the hall to us looking rather pale. He'd disconnected a length of rubber tubing from his distillation apparatus and seen it go up in immediate, vigorous flames. "This stuff makes t-butyllithium look like dishwater" is the statement I remember from that evening. You can buy the pure stuff from Alfa, if you're inclined to run a head-to-head comparison. Do make sure to post the video on YouTube; that's as close as I want to get.
One problem is that it's a pretty volatile compound, boiling at 46C, so there's plenty of vapor around to start a party. The diethyl analog is a bit better, but it's nearly as pyrophoric. The Library of Congress discovered this in the 1980s and 1990s, during a long-running project to deacidify old documents. The diethyl zinc reacts with the acid in aged wood-pulp papers, neutralizing it, lightening the color, and stiffening the paper, so you'd think it would be ideal. Well, except for the instant-bursting-into-ravenous-flames part. Making sure that all the reagent was gone before opening the hatch, that was rather important. The pilot plant for this process suffered from some regrettable explosive bonfires before the whole idea was abandoned. Interestingly, one of the biggest problems seems to have been that the treated books were (at least at first) rather odorous, and some colored book covers were initially affected. You can sense a certain testiness about these issues in the Library's final report on the subject:
It has also been established that tight or loose packing of books; the amount of alkaline reserve; reactions of DEZ with degradation products, unknown paper chemicals and adhesives; phases of the moon and the positions of various planets and constellations do not have any influence on the observed adverse effects of DEZ treatment.
You'll notice that the LOC didn't even bother with the dimethyl compound, and I think I'll take a tip from them.