Find a matching text and replace next two lines in unix

I have a file like this

• aaa
• bbb
• ccc
• ddd
• eee

I want to find bbb and replace next 2 lines with zzz. The final outcome should be

• aaa
• bbb
• zzz
• zzz
• eee

I tried sed, I can do for one line. Not sure how to do it for 2 lines. Please help. Thanks in advance