In Greece:

He tried impressing them by referencing Greek history, which would have worked. The problem was that after his speech, an Azov batallion fighter came up to talk, saying he had Greek descent.

Due to the military Junta they had between 67-74, and the way fascists starved the country in WW2, a lot of people in Greece are very suspicious of fascism, and public opinion was already against Azov and a lot more neutral towards the conflict.

This appearance caused an outcry. Political parties walked out the room en masse, and made proclamations condemning Azov and Zelenski.

In Cyprus: As far as I know, no Azov soldier spoke here (probably because a few hours earlier, the Greece speech happened), but people were still angry that Zelenski did not condemn the Turkish invasion and occupation. This was a comparison to Ukraine that played heavily the last month, in order to create sympathy for Ukraine. Zelenski destroyed that.

In both countries:

People are already mostly against NATO, and now public opinion is swinging against Ukraine.

The Communist Parties of both countries did not attend the speech, and were proven correct in the public eye.

Most political parties are following the examples of Communists, and condemning Zelenski’s speech. There are even questions on who exactly invited him to talk. Nobody seems to know.