Well spotted. I was trying to keep the enquiry general.
However, a connection between the Antelope of the Sixth and the battle of Saragossa/Zaragossa is speculative, as indicated in this footnote from Cannon's Historical Record of Sixth or 1st Warwickshire Regiment to 1838 (one of the earliest references to be found in print:
'Tradition has connected the badge of the ANTELOPE, borne on the colours of the regiment, with its services in Spain; and as the SIXTH captured several colours at SARAGOSSA, which colours were taken to England by their Colonel, THOMAS HARRISON, and presented to Queen Anne, it is not improbable but that an ANTELOPE was on one of the captured colours, and that Colonel HARRISON obtained her Majesty's permission for his regiment to bear the badge of an ANTELOPE in commemoration of the event. No documentary evidence has, however, been met with to substantiaite the tradition. (pp.52-53)
I was following up an earlier assertion in an anonymous letter that appeared in the journal The Royal Military Chronicle from October 1811:
'I have been informed by the present general Campbell, that they took a stand of colours from a Spanish regiment (the royal African) in the battle of Almanza, which had the Antelope for their badge; since which time they have borne it. The general has been upwards of twenty years in the corps, and is therefore likely to know. Sir G. Nugent the present colonel, has in vain made several researches to discover the true origin of its acquisition.'
The author then offers his own theory that the emblem dated from the formation of the 6th in the late C17th when it was raised for service in the United Provinces.
Although no more authoritative than the Cannon history, this letter is interesting for its early reference to Almanza as the Antelope of the Sixth. It should be said that old colonels are the source of many of the most cherished and hoary regimental myths.
More significantly, perhaps, from the link you provided it appears an antelope did not figure in the badge of Regimiento de Africa. Its presence in the Franco-Spanish OB of Saragossa may well be neither here nor there.