After looking a little deeper I will say that it could very well be that the gender of the donkey(s) does not matter at all: for Jerusalem of above is our mother-covenant, (Gal 4:22-27), and has all kinds of symbolic and allegorical significance, (for instance "new Jerusalem" of the Apocalypse would thus be the symbolism of the new covenant and "daughter of Zion-Jerusalem" in the allegory-analogy). Moreover Jerusalem is typed as a wild donkey in Jer 2:23,24 and the daughter of Zion and daughter of Jerusalem has hoofs, (of brass), in Mic 4:13, (again here the scripture speaks of the daughter of Zion and the daughter of Jerusalem as the same, Mic 4:8, just as in Zec 9:9). The Master already had the new covenant during his ministry according to Yohanan:
John 3:27-31 KJV
27 John answered and said, A man can receive nothing, except it be given him from heaven.
28 Ye yourselves bear me witness, that I said, I am not the Christ, but that I am sent before him.
29 He that hath the bride is the bridegroom: but the friend of the bridegroom, which standeth and heareth him, rejoiceth greatly because of the bridegroom's voice: this my joy therefore is fulfilled.
30 He must increase, but I must decrease.
31 He that cometh from above is above all: he that is of the earth is earthly, and speaketh of the earth: he that cometh from heaven is above all.
The Testimony of the Messiah is the new covenant, and his Testimony he received from the heavens, from above, (from the Father without measure, Jhn 3:34), and he that has the bride is the groom: the bride therefore is the new covenant which descends from the heavens, (as in the Apocalypse, it is deep symbolism). However the new covenant is actually a
renewed covenant, and thus the old or primary is the new when it is interpreted through the new revelation of Messiah given to us in his Testimony in the Gospel accounts: in other words they are the same, the Torah, Prophets, and Writings, but understood through the Testimony of Messiah with new "spiritual eyes" given to us through the Testimony of the Messiah. This can be seen in the accounts of the last Seder where there are two of the multiple cups mentioned: Messiah passes not one but two cups around to his disciples, one during the meal and one afterwards, (mentioned in Luke). The first cup is the confirmation of the primary covenant "for many", (Dan 9:27, Mat 26:28 ASV, Mrk 14:24 ASV, Luk 22:17 ASV), while the second cup after the meal is the new covenant, ("shed for you", it is private, personal, and individual, Luk 22:20 ASV). So it may be that the Matthew 21 passage speaks in these terms, that is, Zion-Jerusalem of above, and the daughter of Zion-Jerusalem, (both covenants: one donkey "accustomed to the yoke", and one young-new donkey, regardless of gender because it speaks of heavenly cities, lol).
Galatians 4:22-26
22 For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
23 But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.
24 Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar.
25 For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children.
26 But Jerusalem which is above is free, which is the mother of us all.
These things very well could be . . .
I have much more to study now: thank you Cobra, (sincerely).