Can I bring hair treatment products and shampoo/conditioner over 100ml in my checked luggage?

In the days of the 100ml rule I have yet to take a flight without more than 100ml of shampoo and 100ml of conditioner in a checked bag. It's a complete non-issue, the liquid rules do not apply to checked baggage, only to carry-on.

There is no volume limit for liquids within checked-luggage. It is very common for people to carry liquid cosmetic products since carry-on restrictions very tight. Of course, the total weight of the suitcase has a limit but for a few bottles of shampoo, conditioner, etc you should be able to be within the limit.

More important than the volume is the type of container. Simple plastic bottles or even ones with a spray nozzle are fine but pressurized products are categorized as hazardous material. Aerosols for toiletries are not allowed in large quantities but they may be allowed in small sizes. The FAA specifies a limit but lets airlines add further restrictions and there are different rules outside of the US.

The FAA has a very informative page on the matter for more detail. You did not mention where you will be flying, so if it is outside of the USA, other rules apply for aerosols. For simple plastic or glass bottles that contain shampoo, conditioners, sunscreen, etc, then you can have them in checked luggage.