both China and the Soviet Union were supporting North Vietnam at the same time - up until 1968 (when they had this war over an island). The Sino Soviet split happened much earlier, in 1961.

https://en.wikipedia.org/wiki/China_in_the_Vietnam_War

The great friendship between China and the USA started after that border conflict in 1968, as China was looking for a counterweight.

https://en.wikipedia.org/wiki/Sino-Soviet_border_conflict

I mean Mao was playing Nixon and Kissinger against Brezhnev.

The funny part is where Kissinger is taking all of the credit for the US China rapprochement.