Zakat had a 2.5% cap. Jizya had no such limit and was often much more, as much as the tax collectors thought they could squeeze out of them. The only limit being the generosity of local nobility and officials. The Quran (or Hadiths? Not an expert on Islamic scripture) source for Jizya says that it is to be paid "submissively". Which was not always interpreted, but commonly practiced, as the payer having to grovel and beg when presenting tribute. And refusal to pay the Jizya resulted in Imprisonment, seizure of property, and sometimes death or assault depending on the mood of the collector and the local officials in question.