we are using a ****s oil in a blow moulder and after standing for 6 months not working, the machine was started up and the water content was 305ppm and the zinc was 480ppm.I would like to find out would the water form a gel like substance which would cause rust to form in the hydraulic system.

If you have 305 ppm water in the oil after running I would not worry at all. 305 ppm = 0.035% and is pretty low for hydraulic oil. Anyhow I would check for free water in the drain valve of the reservoir before starting up.
If you have/had free water present you could see rust/corrotion on Iron (or steel) in the water fase.
Another possible problem could be microbacterialogical growth.

The zinc content is present as a part of the oils additive package. Normal