import re

pattern = r"<a?:([^:<>]+)[^<>]*>|:([^:]+):"
def shorten_emojis(content):
    return re.sub(
        pattern, lambda x: f"[{x.group(1)}]" if x.group(1) else f"[{x.group(2)}]"
        ,content
    )

print(shorten_emojis("<a:GG:123456789> <:1Copy:12345678><:14:1256678>:eyes:Hello friend!:eyes:"))
print(shorten_emojis("<a:cryLaptop:738450655395446814><:1Copy:817543814481707030><:14:817543815401439232> <:thoonk:621279654711656448><:coolbutdepressed:621279653675532290><:KL1Heart:585547199480332318>Nice<:dogwonder:621251869058269185> OK:eyes:"))