I broke it into 5 bits and gave odds on each. When you multiply them all out you get tiny, insignificant chance of City winning everything. If you feel that the overall chance of winning CL is 40% then you will be correct but I have it at around 12%.
If you are saying 60% chance of winning League, 40% chance of winning FA Cup and CL is 40% then your maths is good.
We differe because I split the CL into 3 bits. You've got CL odds at 40%, whereas I have them at 0.6 x 0.5 x 0.4 which is 12%. That's where we're different.
No one is right or wrong here. It's just a footballing call on likelihood of outcomes. A domestic treble is significant but unlikely, a quadruple almost impossible. I hope to be proven wrong.