Uiua, 18 17 bytes

/◇⊂⍜▽¯◿2⊛.⊜□≠@A⌵.

Try it

/◇⊂⍜▽¯◿2⊛.⊜□≠@A⌵.­⁡​‎⁠⁠⁠‎⁡⁠⁢⁡⁡‏⁠‎⁡⁠⁢⁡⁢‏‏​⁡⁠⁡‌⁢​‎‎⁡⁠⁤⁢‏⁠‎⁡⁠⁤⁣‏⁠‎⁡⁠⁤⁤‏‏​⁡⁠⁡‌⁣​‎‎⁡⁠⁣⁤‏⁠‎⁡⁠⁤⁡‏‏​⁡⁠⁡‌⁤​‎‎⁡⁠⁣⁡‏⁠‎⁡⁠⁣⁢‏⁠‎⁡⁠⁣⁣‏‏​⁡⁠⁡‌⁢⁡​‎‎⁡⁠⁢⁣‏⁠‎⁡⁠⁢⁤‏‏​⁡⁠⁡‌⁢⁢​‎‎⁡⁠⁤‏⁠‎⁡⁠⁢⁡‏⁠‎⁡⁠⁢⁢‏‏​⁡⁠⁡‌⁢⁣​‎‎⁡⁠⁡‏⁠‎⁡⁠⁢‏⁠‎⁡⁠⁣‏‏​⁡⁠⁡‌­
               ⌵.  # ‎⁡Push an uppercase copy
            ≠@A    # ‎⁢Mask of those not equal to A
          ⊜□       # ‎⁣Partition, boxing each string
        ⊛.         # ‎⁤Copy, push the range 0 to its length
      ◿2           # Modulo 2 (alternating 0s and 1s)
   ⍜▽¯             # ‎⁢⁢At positions with 1s, swapcase
/◇⊂                # ‎⁢⁣Reduce by joining each unboxed string
💎

Created with the help of Luminespire.

I don't like formatting Uiua explanations like this since it's hard to explain everything on one line (especially because I like to do pretty in-depth explanations). Particularly for Uiua it can feel awkward reading the code down and to the left while reading the explanation all the way to the right. But, there's a clear tradeoff, doing explanations this way takes much less time, and I don't have that much time right now so this'll do.

Uiua, 18 17 bytes

/◇⊂⍜▽¯◿2°⊏⊜□≠@A⌵.

Try it

/◇⊂⍜▽¯◿2°⊏⊜□≠@A⌵.­⁡​‎⁠⁠⁠‎⁡⁠⁢⁡⁡‏⁠‎⁡⁠⁢⁡⁢‏‏​⁡⁠⁡‌⁢​‎‎⁡⁠⁤⁢‏⁠‎⁡⁠⁤⁣‏⁠‎⁡⁠⁤⁤‏‏​⁡⁠⁡‌⁣​‎‎⁡⁠⁣⁤‏⁠‎⁡⁠⁤⁡‏‏​⁡⁠⁡‌⁤​‎‎⁡⁠⁣⁡‏⁠‎⁡⁠⁣⁢‏⁠‎⁡⁠⁣⁣‏‏​⁡⁠⁡‌⁢⁡​‎‎⁡⁠⁢⁣‏⁠‎⁡⁠⁢⁤‏‏​⁡⁠⁡‌⁢⁢​‎‎⁡⁠⁤‏⁠‎⁡⁠⁢⁡‏⁠‎⁡⁠⁢⁢‏‏​⁡⁠⁡‌⁢⁣​‎‎⁡⁠⁡‏⁠‎⁡⁠⁢‏⁠‎⁡⁠⁣‏‏​⁡⁠⁡‌­
               ⌵.  # ‎⁡Push an uppercase copy
            ≠@A    # ‎⁢Mask of those not equal to A
          ⊜□       # ‎⁣Partition, boxing each string
        °⊏         # ‎⁤Copy, push the range 0 to its length
      ◿2           # Modulo 2 (alternating 0s and 1s)
   ⍜▽¯             # ‎⁢⁢At positions with 1s, swapcase
/◇⊂                # ‎⁢⁣Reduce by joining each unboxed string
💎

Created with the help of Luminespire.

I don't like formatting Uiua explanations like this since it's hard to explain everything on one line (especially because I like to do pretty in-depth explanations). Particularly for Uiua it can feel awkward reading the code down and to the left while reading the explanation all the way to the right. But, there's a clear tradeoff, doing explanations this way takes much less time, and I don't have that much time right now so this'll do.

Uiua, 18 bytes

/◇⊂⍜▽¯◿2⇡⧻.⊜□≠@A⌵.

Try it

/◇⊂⍜▽¯◿2⇡⧻.⊜□≠@A⌵.­⁡​‎⁠⁠⁠‎⁡⁠⁢⁡⁡‏⁠‎⁡⁠⁢⁡⁢‏‏​⁡⁠⁡‌⁢​‎‎⁡⁠⁤⁢‏⁠‎⁡⁠⁤⁣‏⁠‎⁡⁠⁤⁤‏‏​⁡⁠⁡‌⁣​‎‎⁡⁠⁣⁤‏⁠‎⁡⁠⁤⁡‏‏​⁡⁠⁡‌⁤​‎‎⁡⁠⁣⁡‏⁠‎⁡⁠⁣⁢‏⁠‎⁡⁠⁣⁣‏‏​⁡⁠⁡‌⁢⁡​‎‎⁡⁠⁢⁣‏⁠‎⁡⁠⁢⁤‏‏​⁡⁠⁡‌⁢⁢​‎‎⁡⁠⁤‏⁠‎⁡⁠⁢⁡‏⁠‎⁡⁠⁢⁢‏‏​⁡⁠⁡‌⁢⁣​‎‎⁡⁠⁡‏⁠‎⁡⁠⁢‏⁠‎⁡⁠⁣‏‏​⁡⁠⁡‌­
                ⌵.  # ‎⁡Push an uppercase copy
             ≠@A    # ‎⁢Mask of those not equal to A
           ⊜□       # ‎⁣Partition, boxing each string
        ⇡⧻.         # ‎⁤Copy, push the range 0 to its length
      ◿2            # Modulo 2 (alternating 0s and 1s)
   ⍜▽¯              # ‎⁢⁢At positions with 1s, swapcase
/◇⊂                 # ‎⁢⁣Reduce by joining each unboxed string
💎

Created with the help of Luminespire.

I don't like formatting Uiua explanations like this since it's hard to explain everything on one line (especially because I like to do pretty in-depth explanations). Particularly for Uiua it can feel awkward reading the code down and to the left while reading the explanation all the way to the right. But, there's a clear tradeoff, doing explanations this way takes much less time, and I don't have that much time right now so this'll do.

Uiua, 18 17 bytes

/◇⊂⍜▽¯◿2⊛.⊜□≠@A⌵.

Try it

/◇⊂⍜▽¯◿2⊛.⊜□≠@A⌵.­⁡​‎⁠⁠⁠‎⁡⁠⁢⁡⁡‏⁠‎⁡⁠⁢⁡⁢‏‏​⁡⁠⁡‌⁢​‎‎⁡⁠⁤⁢‏⁠‎⁡⁠⁤⁣‏⁠‎⁡⁠⁤⁤‏‏​⁡⁠⁡‌⁣​‎‎⁡⁠⁣⁤‏⁠‎⁡⁠⁤⁡‏‏​⁡⁠⁡‌⁤​‎‎⁡⁠⁣⁡‏⁠‎⁡⁠⁣⁢‏⁠‎⁡⁠⁣⁣‏‏​⁡⁠⁡‌⁢⁡​‎‎⁡⁠⁢⁣‏⁠‎⁡⁠⁢⁤‏‏​⁡⁠⁡‌⁢⁢​‎‎⁡⁠⁤‏⁠‎⁡⁠⁢⁡‏⁠‎⁡⁠⁢⁢‏‏​⁡⁠⁡‌⁢⁣​‎‎⁡⁠⁡‏⁠‎⁡⁠⁢‏⁠‎⁡⁠⁣‏‏​⁡⁠⁡‌­
               ⌵.  # ‎⁡Push an uppercase copy
            ≠@A    # ‎⁢Mask of those not equal to A
          ⊜□       # ‎⁣Partition, boxing each string
        ⊛.         # ‎⁤Copy, push the range 0 to its length
      ◿2           # Modulo 2 (alternating 0s and 1s)
   ⍜▽¯             # ‎⁢⁢At positions with 1s, swapcase
/◇⊂                # ‎⁢⁣Reduce by joining each unboxed string
💎

Created with the help of Luminespire.

I don't like formatting Uiua explanations like this since it's hard to explain everything on one line (especially because I like to do pretty in-depth explanations). Particularly for Uiua it can feel awkward reading the code down and to the left while reading the explanation all the way to the right. But, there's a clear tradeoff, doing explanations this way takes much less time, and I don't have that much time right now so this'll do.

Uiua, 18 bytes

/◇⊂⍜▽¯◿2⇡⧻.⊜□≠@A⌵.

Try it

Create a mask of non-a/A, partition, create length range mod 2, at swap case at positions with 1s, join together.

Uiua, 18 bytes

/◇⊂⍜▽¯◿2⇡⧻.⊜□≠@A⌵.

Try it

/◇⊂⍜▽¯◿2⇡⧻.⊜□≠@A⌵.­⁡​‎⁠⁠⁠‎⁡⁠⁢⁡⁡‏⁠‎⁡⁠⁢⁡⁢‏‏​⁡⁠⁡‌⁢​‎‎⁡⁠⁤⁢‏⁠‎⁡⁠⁤⁣‏⁠‎⁡⁠⁤⁤‏‏​⁡⁠⁡‌⁣​‎‎⁡⁠⁣⁤‏⁠‎⁡⁠⁤⁡‏‏​⁡⁠⁡‌⁤​‎‎⁡⁠⁣⁡‏⁠‎⁡⁠⁣⁢‏⁠‎⁡⁠⁣⁣‏‏​⁡⁠⁡‌⁢⁡​‎‎⁡⁠⁢⁣‏⁠‎⁡⁠⁢⁤‏‏​⁡⁠⁡‌⁢⁢​‎‎⁡⁠⁤‏⁠‎⁡⁠⁢⁡‏⁠‎⁡⁠⁢⁢‏‏​⁡⁠⁡‌⁢⁣​‎‎⁡⁠⁡‏⁠‎⁡⁠⁢‏⁠‎⁡⁠⁣‏‏​⁡⁠⁡‌­
                ⌵.  # ‎⁡Push an uppercase copy
             ≠@A    # ‎⁢Mask of those not equal to A
           ⊜□       # ‎⁣Partition, boxing each string
        ⇡⧻.         # ‎⁤Copy, push the range 0 to its length
      ◿2            # Modulo 2 (alternating 0s and 1s)
   ⍜▽¯              # ‎⁢⁢At positions with 1s, swapcase
/◇⊂                 # ‎⁢⁣Reduce by joining each unboxed string
💎

Created with the help of Luminespire.

I don't like formatting Uiua explanations like this since it's hard to explain everything on one line (especially because I like to do pretty in-depth explanations). Particularly for Uiua it can feel awkward reading the code down and to the left while reading the explanation all the way to the right. But, there's a clear tradeoff, doing explanations this way takes much less time, and I don't have that much time right now so this'll do.