Sorry for this late response! I cannot myself explain Gomes de Zuara's role in shaping racism, but here are some links to earlier answers by users here on related topics:

• How would an Egyptian in Alexandria at the turn of the millennium have perceived race and skin tone? by u/cleopatra_philopater
• Did the Prophet Muhammad (pbuh) ever say this? by a now-deleted user
• Why are "Moors" often depicted as black in European art? by u/sunagainstgold
• There's been a lot of talk here about how medieval Europe was more racially diverse than we think. Would it be out of the question to see a white person in 1000s-1300s Sub-Saharan Africa? by u/labarge3
• Europe had normal diplomatic relations with non-white nations before turning explosively racist to justify their actions against all others. What happened to cause this shift? by u/victoryfanfare
• How do contemporary academics who say that race and racism date to the Enlightenment explain what seem to be examples of racial categorization, racial stereotyping and racial prejudice in ancient literature and art? by u/restricteddata and u/PhiloSpo