12/31/2019
OoT:       16:58 Torje
MM:        28:17 EnNopp112
TWW:     1:04:50 Linkus7
TP:      2:54:11 Demon
SS:      2:09:22 sva
BotW:      27:29 sketodara01417
OoT3D:     29:28 ZeldaCubed
MM3D:    1:24:17 iwabi74
TWWHD:     54:15 Ian Miles
TPHD:    3:26:31 Jacquaid
Total:  13:36:42

12/31/2021
OoT:        6:49 PaintSkate8
MM:        18:37 raggen
TWW:       53:08 iwabi74
TP:      2:51:06 Demon
SS:      1:21:49 sva
BotW:      24:56 Player_5
OoT3D:     27:50 pal62
MM3D:      33:23 iwabi74
TWWHD:     47:14 mralberto23
TPHD:    3:15:48 gymnast86
SSHD:    4:42:18 gymnast86
Total:  15:42:58

Some Notable Improvements:
Ocarina of Time:
By the end of 2019, we already knew that this was coming. The discovery of Stale Reference Manipulation in October led to the first applications of Arbitrary Code Execution by November. ACE was shown off at AGDQ in January 2020, and by January 15th, ACE was used to warp to the credits from Kokiri Forest in less than 13 minutes. The any% strategy has been through many iterations over the last two years, ultimately leading to the current route which grabs the Kokiri Sword, makes one trip to the Kokiri Shop, and then warps directly to the credits.

Majora's Mask:
Like OoT, the SRM/ACE any% route for Majora's Mask was iterated upon, including a route which would warp to the credits from the Astral Observatory shortly after beginning the second cycle. But, despite all of the SRM related discoveries, there was still no way to avoid completing the first cycle to become Human Link before beating the game. That changed in November 2021, when a method was found to use SRM/ACE in North Clock Town as Deku Link to become Human Link early, finally delivering on one of the long-recognized Holy Grails of 3D Zelda speedruns, and bringing the any% time below 20 minutes.

The Wind Waker:
So... it turns out that all you need to do to push Link through the Hyrule barrier is to just drop a bomb while standing where the two walls meet. (Okay, it's actually incredibly precise. It is so precise, that when this same strategy was run through thousands of simulations way back in 2017, no solutions were found due to using a very slightly too small speed for the bomb push, illustrating just how close this is to not working.)

Skyward Sword:
In June 2020, the discovery of Early Boss Rush made it possible to set certain story flags early, allowing runners to skip Ancient Cistern, Fire Sanctuary, and the Imprisoned 2 (kind of).

Majora's Mask 3D:
In March 2021, a method was discovered to warp directly to the fight with Majora from Deku Palace using SRM, skipping all four dungeons and finishing the game shortly after completing the first cycle to become Human Link. As of now, this remains the only usage of SRM that has been implemented into a speedrun of one of the 3DS remakes! Another fun fact: Although this route finally ended the 2.5 year long standing any% record held by iwabi, iwabi's record-holding streak was never broken, as he managed to stay ahead of everybody else with the SRM route. Iwabi has held the any% record for MM3D, uninterrupted, since September of 2016.

Final thoughts:
Unfortunately, the improvements of the last 2 years have not been enough to counter-balance the release of Skyward Sword HD! But actually though, in the last 2 years, we have seen:

-3 hour barriers broken (TWW, SS, MM3D)
-2 "Holy Grails" newly implemented (MM First Cycle Skip, MM3D Moon Warp)
-6 new dungeons skipped (2 in SS, 4 in MM3D. Kind of 1 in OoT, but not really)
-More than 2.5 hours taken off the games which had been released before 2020

Pretty cool!