In order to understand better, I made solutions with different amounts of ZnSO4 to dissolve in 200 ml of water (3.2, 1.6, 1.4, 1.2, 1.0, 0.8, 0.6, 0.4 and 0.3. There were no precipitate for the solutions containing 0.4 g/200 ml water and 0.3 g/200 ml water, however the solution was not clear. In teh other solutions, the amount of precipitate was less when the solution concentration was smaller.

I know that ZnSO4 id highly soluble in water, so how can I explain this ?