While this set of Cantonese initials are similar to the Putonghua set, the difference is still audible. Beginners of Cantonese should carefully distinguish the two sets. Remember, practice makes perfect!
1. The Cantonese /z-/ is more retracted than the Putonghua [z], though they are both unaspirated. This sound is almost like the English ‘ts’ in ‘casts’.
2. The Cantonese /c-/ is more retracted than the Putonghua [c], though they are both aspirated. This sound is almost like the English ‘ts’ in ‘cats’.
For English speakers, note the slight difference in aspiration between the ‘ts’ in unaspirated ‘casts’ and aspirated ‘cats’.
3. The Cantonese /s-/ is more retracted than the Putonghua [s], like the English ‘s’.
Note that for many speakers, there is free variation of Cantonese /z- c- s-/, which means they can be even more retracted. For more, see ‘Further Reading: Free Variation in Cantonese – Free Variation in /z- c- s-/’.
As to aspiration, see ‘Cantonese Characteristics - Aspiration’.