Complex sentence: This also marked the first time that all three New York NHL teams made the playoffs in the same season, a feat which has since been repeated twice more: in the 1993-94 NHL season and the 2006-2007 NHL season.
Split into simpler sentences: This also marked the first time that all three New York NHL teams made the playoffs in the same season. A feat which would be repeated only twice more in the 1993-94 NHL season and the 2006-2007 NHL season.