"A Shalom Zachar is not held when this Friday night coincides with the night of Yom Kippur or the night of the Passover Seder.»
Besides the common absence of Shalom Zachar consider these other common factors
1. Wearing a Kittel
2. Diet is restricted on both
3. Minhaggim to stay up late - EG Shir Hashirim or Shir Hayichud
4. Preceded by D'rashot: Shabbat Hagadol, Shabbat Shuvah
5 L'shanah haba'ah recited Seder Night and N'ilah night
6. Shirah said the same week Shirat Haazinu, Shirat Hayyam, sometimes sharing same Haftarah
7. Special Haftarah, both without a special Maftir.
Hag Kasher v'Samei'ach!