I really can understand why LZ choose to forgave her 10 years ago, but not now. She probably tell him she regret what she did, and vow never do it again. LZ gave her a chance. For 10 years, it appears she kept her promise, so they went on having baby, etc. Only to find she never stopped (which implies she never regreted) and this push him over the edge...
all right, good night. Have a nice sleep~~~