i have been mixing it this way for years now and never had a problem i only put 3 drops out of a syrenge with a needle on it in 20 cc of valbazen, im not trying to say your wrong but can you tell me why it would hurt them, i was told years ago that valbazen gets everything but one or two types of worms and the ivomec takes care of them. i dont know if its the mixture or if we have just never had any worm infestation but my chickens are all fat and happy. again not trying to say you are wrong but would like to learn more if you wouldnt care to teach me.
If you're using ivomec injectable, it may be an effective wormer on other livestock, but not chickens;
http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0450.1989.tb00635.x/abstract
It will still kill mites in chickens. Ivermectin pour on and eprinex have been losing their effectiveness on large roundworms and wont kill cecal worms. This is due to its overuse as a miteacide, causing wormer resistance over time. I recently read where ivermectin is useless treating capillary worms, I 'll see if I can find the link and reference it for you.
Ivomec products can stay in the chickens system for a longer period of time, the longer the residue actually stays in the system, the greater the chance of eventual organ failure. The link I had showing this is no longer available, sorry.
Valbazen is a much safer wormer and kills all known worms that chickens can get including flukes. It slowly kills worms over a 3-5 day period preventing toxic worm overload. When valbazen is redosed 10 days later to kill worm larva hatched since the initail dosing, the kill rate is nearly 100% except for possibly gapeworm and tapeworms which may require several more wormings and at a higher dose.
http://japr.fass.org/content/16/3/392.full
I recommend that you continue with valbazen and add safeguard (fenbendazole) to your inventory and only use ivomec for treating mites.
You can give the valbazen orally undiluted if you wish, 1/2cc for standards, 1/4cc for smaller birds...and get the same results as mixing it in water. This is up to you of course. If you wish to continue doing what you're doing, that's up to you as well.
Here's a link about ivomec not being effective in peafowl against capillary worms. Panacur (fenbendazole aka safeguard) is recommended. FYI only:
http://peafowlareus.com/worming.asp