This is a PIA job. Here's some help, but before you start, might I ask why.

Unbuild w/o warping the rims.
Start by slackening all the left side spokes 1 full turn, 1/2 turn at a time, going around twice. This will detention the wheel somewhat, while still leaving enough tension to help you later on. Next slacken the right spokes 1/2 turn at a time working around, until slack, then remove the nipples entirely.

You can push the outside spokes through, but removing the inside spokes is easiest if you cut them near the flange. Use one of the outside spokes to confirm the length for the replacements.

Start relacing
Take 1/2 of the replacement spokes and gently curve them by pulling them through your fingers, so that when pushed through they can be lead out past the outermost cross on the opposite side. If you curve them carefully without any kinks, they'll straighten nicely when tensioned, otherwise straighten them as well as possible, but it's better to leave some curve than to put any kinks in. Push through the outer spokes.

Lay the wheel flat and bring all the inner spokes out toward the rim sort of parallel with their opposite flange mates, and let them drop into the appropriate gap. Repeat for the outers. Now lace them in crossed pairs, so you won't have to drag them past each other and possibly scratch the rim. The crossed pairs are 3 holes apart for 1 cross, 5 for 2x 7 for 3x and 9 for 4x. They should already be in the right place. Double check the phasing to the opposite flange, lace the outer under the inner and attach the 2 nipples, move to the next pair, and so on until finished. The right holes will be obvious because the crossed pairs will appear equal in length.

Now that the wheel is laced, tighten all to a set somewhat slack but equal length using a reference, such as one thread showing outside the nipple. Then tighten by degrees, counting turns and working your way around until there's some tension, and proceed as with any other build from there out.

Note, one trick I use that's not in most, if any tutorials is to build the wheel overdished to the right slightly, then add final tension from the left only as you bring it to center. This reduces the amount of work on the tighter right side spokes.

Good luck.