Manchester City is going to face Bournemouth in the quarter-finals of the FA Cup. Bournemouth is not a weak team this season. Also , Bournemouth won the last match against Manchester city by 2-1. So it will be very difficult for city to win against bournemouth. Also , City may face Aston Villa/nottingham Forest or Brighton in the semi-finals or final. It is very difficult for City to win against these teams. If City's performance does not become stable , it is impossible for Manchester City to win the FA Cup title.
Of course it is not easy for Manchester City to win the FA Cup, but this is the only chance they have right now so Pep Guardiola will definitely do his best.
Pep Guardiola's step this season are a little more difficult because their inconsistent performance has made several opportunities to win the title disappear.
The FA Cup will be the only one they can possibly achieve if they can perform consistently until the final, although the struggle to qualify for the final itself will be a little more difficult against several teams.
But I am sure they will do their best to get the title because Pep Guardiola has to do his best in the opportunity they have.